Health-Related Quality of Life in Individuals With Chronic Ankle Instability

Context:

Individuals with chronic ankle instability (CAI) have reported decreased global and regional function. Despite the identification of functional deficits in those with CAI, more research is required to determine the extent to which CAI influences the multidimensional profile of health-related quality of life.

Objective:

To determine whether global, regional, and psychological health-related outcomes differ between individuals with and without CAI.

Design:

Case-control study.

Setting:

Laboratory.

Patients or Other Participants:

Twenty-five participants with CAI (age = 21.9 ± 2.5 years, height = 170.8 ± 8.6 cm, mass = 69.8.0 ± 11.7 kg) were sex- and limb-matched to 25 healthy participants (age = 22.0 ± 2.1 years, height = 167.4 ± 9.1 cm, mass = 64.8 ± 11.2 kg).

Main Outcome Measure(s):

Both groups completed the Disablement in the Physically Active Scale, the Foot and Ankle Ability Measure (FAAM), the FAAM-Sport, the Tampa Scale of Kinesiophobia-11, and the Fear-Avoidance Beliefs Questionnaire. Dependent variables were scores on these instruments, and the independent variable was group.

Results:

Compared with healthy individuals, those with CAI reported decreased function on the Disablement in the Physically Active Scale, FAAM, and FAAM-Sport (P < .001) and increased fear of reinjury on the Tampa Scale of Kinesiophobia-11 and Fear-Avoidance Beliefs Questionnaire (P < .001). In the CAI group, the FAAM and FAAM-Sport demonstrated a significant relationship (r = 0.774, P < .01).

Conclusions:

Individuals with CAI reported decreased function and increased fear of reinjury compared with healthy control participants. Also, within the CAI group, there was a strong relationship between FAAM and FAAM-Sport scores but not between any other instruments. These findings suggest that health-related quality of life should be examined during the rehabilitation process of individuals with CAI.Key Words: ankle sprains, impairment, fear of reinjury, psychology

Key Points

• Individuals with chronic ankle instability reported global, regional, and psychological health-related quality-of-life deficits compared with healthy control participants.
• Functional deficits and psychological barriers reported by the patient should be taken into consideration when clinicians treat individuals with chronic ankle instability.

Individuals around the globe engage in physical activity for personal interest or general health and fitness, subjecting the ankle to various conditions in which injury could occur. Roughly one-half of all ankle sprains in the United States occur during athletic activity,^1,2 and an estimated 3 million patients with ankle sprains and strains seek treatment in hospital emergency departments or in a physician''s office each year.³ Within the past decade, ankle sprains have represented approximately 80% of ankle injuries in athletes^4,5 and military cadets,¹ resulting in immense health care costs. Further contributing to the problem, up to 74% of patients who sustain a single ankle sprain go on to develop residual symptoms that may persist years after the initial injury,⁶ with many developing chronic ankle instability (CAI).^7–9 Chronic ankle instability, or recurring ankle sprains and repetitive giving way of the ankle during functional activities, has been linked to both mechanical and functional impairments.¹⁰ Those impairments are thought to contribute to long-term limitations and restrictions in recreational and occupational activities that consequently affect health-related quality of life (HRQOL).^9,11Encompassing social, physical, and psychological health components, HRQOL is a multidimensional approach to health care¹² that has become an integral part of health surveillance. Because of the multidimensional nature of HRQOL, a variety of self-reported instruments have been designed to measure global, regional, and psychological health components. Global instruments (also known as generic instruments) are nonspecific to body region or condition and designed to assess the patient''s overall health, whereas regional instruments can be specific to a joint or region of the body, such as the lower extremity.¹³ Psychological instruments capture various aspects of the patient''s mental or social function, such as fear of reinjury. Fear of reinjury is the concept of fear after injury and includes but is not limited to kinesiophobia, fear-avoidance beliefs, or reinjury anxiety. Self-reported instruments enhance the clinician''s ability to incorporate patient values and perspectives and are a vital component of the evidence-based practice model.¹⁴Chronic ankle instability has been associated with decreased HRQOL based on global and regional outcomes.^15,16 Individuals with CAI have reported decreased global function on the Short Form-36 (SF-36).¹⁶ Furthermore, Arnold et al¹⁶ found a moderately positive correlation between SF-36 Physical Function domain scores and the Foot and Ankle Ability Measure (FAAM), a regional measure of function that includes both Activities of Daily Living (FAAM-ADL) and Sport subscales (FAAM-Sport). This relationship suggests that CAI may reduce overall HRQOL. Individuals with CAI have also reported decreased function on other regional instruments, such as the Ankle Joint Functional Assessment Tool, Foot and Ankle Disability Index (FADI), and FADI-Sport.^15,17–19 On a variety of self-reported instruments, both global and regional deficits have been detected in physically active individuals with CAI.Despite identifying global and regional HRQOL deficits in those with CAI, more research is required to determine the extent to which CAI influences the multidimensional profile of HRQOL. Therefore, examining global function using a scale designed for physically active individuals or psychological measures, such as kinesiophobia and fear-avoidance beliefs, could reveal more about the condition. To our knowledge, scores on the Disablement in the Physically Active Scale (DPA), Tampa Scale of Kinesiophobia-11 (TSK-11), and Fear-Avoidance Beliefs Questionnaire (FABQ) have yet to be examined in the CAI population. Using instruments that encompass the multidimensional profile of HRQOL will enhance the clinician''s ability to incorporate patient values and perspectives into rehabilitation and outcomes assessment.Although fear of reinjury has been associated with a variety of orthopaedic conditions,^20–23 little evidence supports the presence of kinesiophobia or fear-avoidance beliefs in patients with CAI. Wikstrom²⁴ reported that TSK-17 scores did not differ between individuals with CAI and “copers”; however, both groups reported elevated levels of kinesiophobia. Left unaddressed, global and regional functional deficits, as well as fears of reinjury, may contribute to long-term consequences associated with CAI, such as degenerative joint disease²⁵ and decreased physical activity.⁹ Therefore, the primary purpose of our investigation was to determine whether global, regional, and psychological health outcomes differed between individuals with and without CAI. The secondary purpose was to examine relationships among instruments and between injury-history characteristics and instrument scores in the CAI group. We hypothesized that individuals with CAI would exhibit decreased global and regional function and increased fear of reinjury compared with healthy individuals. Additionally, we proposed that relationships would exist among health-related outcomes instruments and between injury-history characteristics and instrument scores.     

Postural-Stability Tests That Identify Individuals With Chronic Ankle Instability

Context:

Chronic ankle instability (CAI) is characterized by repeated ankle sprains, which have been linked to postural instability. Therefore, it is important for clinicians to identify individuals with CAI who can benefit from rehabilitation.

Objective:

To assess the likelihood that CAI participants will exhibit impaired postural stability and that healthy control participants will exhibit better test performance values.

Design:

Case-control study.

Setting:

Laboratory.

Patients or Other Participants:

People with CAI (n = 17, age = 23 ± 4 years, height = 168 ± 9 cm, weight = 68 ± 12 kg) who reported ankle “giving-way” sensations and healthy volunteers (n = 17, age = 23 ± 3 years, height = 168 ± 8 cm, weight = 66 ± 12 kg).

Intervention(s):

Participants performed 7 balance tests: Balance Error Scoring System (BESS), time in balance, foot lift, single-legged stance on a force plate, Star Excursion Balance Test, side hop, and figure-of-8 hop.

Main Outcome Measure(s):

Balance was quantified with errors (score) for the BESS, length of time balancing (seconds) for time-in-balance test, frequency of foot lifts (score) for foot-lift test, velocity (cm/s) for all center-of-pressure velocity measures, excursion (cm) for center-of-pressure excursion measures, area (cm²) for 95% confidence ellipse center-of-pressure area and center-of-pressure rectangular area, time (seconds) for anterior-posterior and medial-lateral time-to-boundary (TTB) measures, distance reached (cm) for Star Excursion Balance Test, and time (seconds) to complete side-hop and figure-of-8 hop tests. We calculated area-under-the-curve values and cutoff scores and used the odds ratio to determine if those with and without CAI could be distinguished using cutoff scores.

Results:

We found significant area-under-the-curve values for 4 static noninstrumented measures, 3 force-plate measures, and 3 functional measures. Significant cutoff scores were noted for the time-in-balance test (≤25.89 seconds), foot-lift test (≥5), single-legged stance on the firm surface (≥3 errors) and total (≥14 errors) on the BESS, center-of-pressure resultant velocity (≥1.56 cm/s), standard deviations for medial-lateral (≤1.56 seconds) time-to-boundary and anterior-posterior (≤3.78 seconds) time-to-boundary test, posteromedial direction on the Star Excursion Balance Test (≤0.91), side-hop test (≥12.88 seconds), and figure-of-8 hop test (≥17.36 seconds).

Conclusions:

Clinicians can use any of the 10 significant measures with their associated cutoff scores to identify those who could benefit from rehabilitation that reestablishes postural stability.Key Words: lower extremity, ankle sprains, Balance Error Scoring System, Star Excursion Balance Test

Key Points

• Chronic ankle instability has been linked to postural instability. Postural instability can be addressed with targeted interventions.
• The time-in-balance test, foot-lift test, Balance Error Scoring System total and single-limb stance on a firm surface, center-of-pressure resultant velocity, time-to-boundary anterior-posterior and medial-lateral standard deviation, Star Excursion Balance Test in the posteromedial direction, side-hop test, and figure-of-8 hop test can be used to identify people with chronic ankle instability who may benefit from rehabilitation to reestablish postural stability.

Ankle sprains are one of the most common injuries experienced by the physically active.^1–3 A single ankle sprain can lead to balance impairments, recurrent instability, and recurrent sprains.^4,5 These deficits are often grouped together and defined as chronic ankle instability (CAI), which is more specifically defined by a history of ankle sprains or recurrent episodes of instability or both.⁶ Clinicians and researchers alike focus on identifying and correcting balance impairments because poor balance is linked to ankle sprains.⁷A variety of postural-stability tests have been developed to identify poor balance associated with CAI⁴ in both clinical and research settings. Tests include the Balance Error Scoring System (BESS), time-in-balance test, foot-lift test, force-plate measures (eg, center-of-pressure velocity, center-of-pressure area, time to boundary),⁴ and functional measures (eg, Star Excursion Balance Test [SEBT],⁸ side-hop test, figure-of-8 hop test).⁹ Several authors^10–12 have performed receiver operating characteristic (ROC) curve analyses and established cutoff scores for a number of static postural control variables in those with ankle instability. However, no investigators to our knowledge have determined the likelihood that patients with CAI will exhibit impaired postural stability, both statically and functionally, in the same cohort.Clinical tests focus on noninstrumented measures that quantify balance. Common static, clinician-based postural-stability tests include the BESS, time-in-balance test, and foot-lift test. Researchers^13–15 have also attempted to develop the most precise measurements of static balance using instrumented force plates. However, force plates can be expensive and may not be readily available to clinicians. Several center-of-pressure (COP) measurements have been used by investigators^13,16 to detect balance deficits associated with CAI.Some authors^17,18 have suggested that functional tests may provide better means of identifying participants with CAI than static, single-legged balance tests because functional movements may magnify the degree to which sensorimotor deficits affect balance performance. Functional balance tests may provide an overall assessment of joint stability, strength, and sensorimotor function, which might help clinicians identify balance deficits that would be undetected with static tests.⁹ Functional balance tests are often used clinically to determine readiness for returning to physical activity, but clinicians may also use established cutoff scores of functional tests to identify patients with postural instability who would benefit from rehabilitation.Researchers⁹ have also suggested that functional balance tests that increase inversion torques on the ankle joint can identify performance deficits associated with CAI. Furthermore, these tests can be administered quickly and easily with minimal supplies. However, on several functional measures (ie, up-down hop, single hop,⁹ triple-crossover hop for distance, and shuttle run¹⁹), no difference was seen between those with CAI and those with healthy ankles. Given the conflicting results in this area, functional testing warrants further investigation.Due to the large number of balance assessments, we believe that clinicians should know the type of postural-stability tests and outcomes that are most appropriate to discriminate between those with CAI and those with stable ankles. Therefore, the purpose of our study was to assess the likelihood that CAI participants would exhibit impaired postural stability and that healthy control participants would exhibit better outcomes identified by specific cutoff values. With this information, clinicians can identify individuals who may benefit from rehabilitation that reestablishes postural stability. This finding is important because of similarities to a subgroup of patients in the anterior cruciate ligament injury literature; there are “copers” who do not demonstrate postural instability and therefore do not require rehabilitation.²⁰ Furthermore, clinicians can benefit from knowing minimum test performance goals for CAI patients that correspond to the cutoff points that separate those with CAI and healthy ankles.     

Alterations in Neuromuscular Control at the Knee in Individuals With Chronic Ankle Instability

Context:

Few authors have assessed neuromuscular knee-stabilization strategies in individuals with chronic ankle instability (CAI) during functional activities.

Objective:

To investigate the influence of CAI on neuromuscular characteristics around the knee during a stop-jump task.

Design:

Case-control study.

Setting:

Research laboratory.

Participants or Other Participants:

A total of 19 participants with self-reported unilateral CAI and 19 healthy control participants volunteered for this study.

Intervention(s):

Participants performed double-legged, vertical stop-jump tasks onto a force plate, and we measured muscle activation around the knee of each limb.

Main Outcome Measure(s):

We calculated the integrated electromyography for the vastus medialis oblique, vastus lateralis, medial hamstrings, and lateral hamstrings muscles during the 100 ms before and after initial foot contacts with the force plate and normalized by the ensemble peak electromyographic value. Knee sagittal-plane kinematics were also analyzed during a stop-jump task.

Results:

Compared with control participants, the CAI group demonstrated greater prelanding integrated electromyographic activity of the vastus medialis oblique (CAI = 52.28 ± 11.25%·ms, control = 43.90 ± 10.13%·ms, t₃₆ = 2.41, P = .021, effect size = 0.78, 95% confidence interval = 0.11, 1.43) and less knee-flexion angle at the point of initial foot contact (CAI = 7.81° ± 8.27°, control = 14.09° ± 8.7°, t₃₆ = −2.28, P = .029, effect size = −0.74, 95% confidence interval = −1.38, −0.07) and at 100 ms post–initial foot contact (CAI = 51.36° ± 5.29°, control = 58.66° ± 7.66°, t₃₆ = −3.42, P = .002, effect size = −1.11, 95% confidence interval = −1.77, −0.40). No significant results were noted for the other electromyographic measures.

Conclusions:

We found altered feed-forward patterns of the vastus medialis oblique and altered postlanding knee sagittal-plane kinematics in the CAI group. These observations may provide insight regarding sensorimotor characteristics that may be associated with CAI.Key Words: feed-forward pattern, feedback, sensorimotor control

Key Points

• Increased preparatory vastus medialis oblique muscle activation and decreased postlanding knee-flexion angle were seen in participants with chronic ankle instability compared with the control group during a vertical stop jump.
• Feed-forward sensorimotor control around the knee should be addressed during therapeutic interventions for chronic ankle instability.

Chronic ankle instability (CAI) is common after an acute lateral ankle sprain (LAS) in physically active individuals,^1–3 leading to self-assessed disability and decreased quality of life.⁴ It has been reported that CAI is a leading factor for the development of posttraumatic osteoarthritis in the ankle,^1,5 requiring costly medical diagnostic techniques and extensive treatments. With a high rate of recurrence plus the complications of prolonged functional impairments after ankle sprains, there is an increased need for evidence-based practice to develop and implement more effective intervention programs for CAI.One important step in reducing the recurrence rate is to understand the underlying sensorimotor mechanisms for CAI. After LAS, altered afferent inputs from the somatosensory system around the ankle and central changes in sensorimotor control may result in proximal joint adaptations to compensate for residual symptoms and functional impairments.^6–13 Previous researchers^6,10 have indirectly assessed sensorimotor control strategies in CAI patients at the knee using sagittal-plane kinematics. Gribble and Robinson⁶ found greater knee extension before and at the point of ground impact⁷ during a vertical jump-landing task, whereas Caulfield and Garrett¹⁰ observed greater knee flexion before and after landing during a drop-jump task. These contradictory findings may be attributable to differences between these studies in the demands of the jump-landing tasks; however, neither group quantified electromyography (EMG) of the knee musculature during the landing tasks. Thus, we still do not know how activation of the knee flexors and extensors influences sagittal-plane kinematics during jump-landing tasks in individuals with a history of ankle injury.Although several EMG investigations have demonstrated altered preparatory muscle-activation patterns in the ankle during jump landings in CAI patients,^9,11–14 few investigators have examined preparatory EMG measures in the knee during a dynamic task within this population, which may limit our estimation of relative preparatory activity of muscles in the knee. Delahunt et al¹¹ observed an increase in rectus femoris activation before ground impact during a lateral-hop task in individuals with CAI, supporting modified preprogrammed muscle-activation patterns via feed-forward motor control to prepare for ground impact. Additionally, Delahunt et al¹⁴ reported that those with CAI exhibited no differences in preparatory rectus femoris muscle activation during a drop-landing task. However, a drop-jump task is not a sport-related functional task and does not necessarily replicate the potential mechanism of injury.Whereas a relationship between CAI and altered biomechanical patterns at the knee has been established, few authors have quantitatively assessed sensorimotor control strategies at the knee using EMG while measuring sagittal-plane kinematics in individuals with CAI during other high-risk and sport-related functional activities, such as a vertical stop jump. It is important to examine knee muscle activation and sagittal-plane kinematic patterns to determine the potential effect of CAI on the sensorimotor control mechanism, especially pre-event decisions and postevent reactions, during a stop-jump maneuver. Researchers^6,10 have speculated that adapted feed-forward sensorimotor control strategies at the knee associated with CAI could be a way to protect the unstable ankle by controlling the position of the ankle and center of mass on ground impact. However, a diminished level of dynamic stability and energy dissipation of the knee musculature after landing has been observed in individuals with CAI.^6,7,15 Therefore, this proposed protective response to the unstable ankle may not be an efficient response. Although information is limited, there is a potential link between a history of ankle sprain and risk of injury at the knee joint.^16–18 The potential sensorimotor adaptations associated with CAI may not necessarily be protective for other joints. Identifying an underlying relationship between CAI and compensatory sensorimotor control in the knee may help clinicians and researchers to develop more comprehensive interventions to enhance global coordination in those with CAI and prevent future injury. Thus, the purpose of our study was to examine individuals with and without unilateral CAI for the presence of altered neuromuscular control in the knee during a vertical stop jump. Previous investigators observed a smaller knee-flexion angle before and after ground impact during a jump-landing task in participants with CAI compared with healthy controls.^6,7,19 Furthermore, increased preparatory muscle activation in the ankle during a stop-jump task has been reported in those with CAI.¹² Our hypotheses were that, during a stop-jump task, participants with CAI would demonstrate (1) increased quadriceps muscle activation before and after landing; (2) increased hamstrings muscle activation before landing; (3) decreased hamstrings muscle activation after landing; and (4) reduced knee-flexion angle before and after landing, as compared with participants without CAI.     

Patient-Reported Outcome Measures in Individuals With Chronic Ankle Instability: A Systematic Review

Context A comprehensive systematic literature review of the health-related quality-of-life (HRQOL) differences among individuals with chronic ankle instability (CAI), ankle-sprain copers, and healthy control participants has not been conducted. It could provide a better indication of the self-reported deficits that may be present in individuals with CAI.Objective To systematically summarize the extent to which HRQOL deficits are present in individuals with CAI.Conclusions The evidence suggested that CAI is associated with functional and HRQOL deficits, particularly when examined with region-specific PROs. However, PROs do not appear to differ between copers and healthy controls.Key Words: region-specific outcomes, ankle sprains, patient-centered care

Key Points

• Chronic ankle instability (CAI) is most likely associated with decreased health-related quality of life as measured by patient-reported outcomes.
• Patient-reported outcomes did not appear to be affected in ankle-sprain copers.
• Given that region-specific outcomes were worse in individuals with CAI than in ankle-sprain copers and healthy control participants, they should be considered when treating CAI and ankle sprains.

Ankle sprains are the most commonly reported injury in collegiate and high school athletics, accounting for roughly 16% of all injuries^1,2; however, other estimates have indicated that ankle sprains compose up to 45% of all athletic injuries.^3,4 These injuries have placed an enormous burden on the health care industry, with an estimated $4.4 billion spent annually on treatment.⁵ Not only are ankle sprains prevalent and costly injuries, at least one third of individuals who sustain acute ankle sprains will develop chronic ankle instability (CAI).^6–8 This condition is characterized by residual symptoms that include feelings of “giving way” and instability, recurrent ankle sprains, and functional loss after 1 or more acute ankle sprains.⁹ Residual symptoms associated with CAI can persist for decades,¹⁰ making it difficult for an individual to lead an active, healthy lifestyle. Furthermore, the repetitive trauma associated with recurrent ankle sprains often contributes to more advanced conditions, such as ankle osteoarthritis,¹¹ for which effective treatments are lacking.Traditionally, CAI research has focused primarily on the pathophysiology of this condition by concentrating efforts on identifying mechanical and functional insufficiencies from a disease-oriented perspective.^12–14 In the last decade, researchers¹⁵ have expanded their efforts to include the patient''s perception of his or her health status, as patient-based outcomes are increasingly recognized in health care. These changes have led to the development of several patient-reported outcomes (PROs) to measure functional limitations in patients with CAI, including the Ankle Joint Functional Assessment Tool (AJFAT),¹⁶ Foot and Ankle Ability Measure (FAAM),¹⁷ and Chronic Ankle Instability Scale.¹⁸ These 3 instruments are self-reported and have been used for many ankle conditions. Their development has enabled researchers and clinicians to collect outcomes that examine a range of activities of daily living (ADLs) and sport tasks from the patient''s perspective.In the CAI literature, both discriminative (eg, Ankle Instability Instrument,¹⁹ Cumberland Ankle Instability Tool [CAIT])²⁰ and evaluative (eg, FAAM) PROs have been used. Discriminative instruments are used to identify individuals with a particular pathologic condition (eg, CAI), whereas evaluative instruments measure an individual''s perceived level of function.²¹ Donahue et al²² reviewed 7 instruments used to discriminate between participants with and without CAI and recommended both the CAIT and Ankle Instability Instrument to determine ankle-stability status. Furthermore, Eechaute et al²³ assessed the clinimetric qualities of 4 evaluative instruments and concluded that the Foot and Ankle Disability Index (FADI) and FAAM were the most appropriate tools for quantifying functional limitations in patients with CAI. Despite these findings, the use of PROs has been inconsistent in the CAI literature. To strengthen the reporting of CAI participant information and to further our knowledge about the limitations associated with this condition, the International Ankle Consortium²⁴ recently released a position statement in which it endorsed specific patient-selection criteria for CAI research and advocated for the use of PROs to better describe this population. In addition to the discriminatory and evaluative instruments used to quantify region-specific function in individuals with CAI, other investigators^25,26 have used PROs to measure health-related quality of life (HRQOL) via generic and dimension-specific instruments. Therefore, further examining PROs used in the CAI literature may allow us to better describe the population and improve our understanding of the condition for future research and clinical practice.A variety of PROs have been used to compare HRQOL in individuals with CAI and ankle-sprain copers (ie, individuals with a history of 1 ankle sprain and no residual symptoms) or healthy control participants. Compared with ankle-sprain copers and healthy populations, individuals with CAI appear to exhibit HRQOL deficits.²⁵ However, to our knowledge, a comprehensive review of the differences among groups has not been conducted. Providing a comprehensive systematic review that critically appraises the research literature may offer a better indication of the self-reported deficits that may be present in those with CAI. Therefore, the purpose of our systematic review was to determine the extent to which HRQOL deficits are present in individuals with CAI.     

Biomechanical Response to External Biofeedback During Functional Tasks in Individuals With Chronic Ankle Instability

ContextAltered biomechanics displayed by individuals with chronic ankle instability (CAI) is a possible cause of recurring injuries and posttraumatic osteoarthritis. Current interventions are unable to modify aberrant biomechanics, leading to research efforts to determine if real-time external biofeedback can result in changes.ObjectiveTo determine the real-time effects of visual and auditory biofeedback on functional-task biomechanics in individuals with CAI.DesignCrossover study.SettingLaboratory.Patients or Other ParticipantsNineteen physically active adults with CAI (7 men, 12 women; age = 23.95 ± 5.52 years, height = 168.87 ± 6.94 cm, mass = 74.74 ± 15.41 kg).Intervention(s)Participants randomly performed single-limb static balance, step downs, lateral hops, and forward lunges during a baseline and 2 biofeedback conditions. Visual biofeedback was given through a crossline laser secured to the dorsum of the foot. Auditory biofeedback was given through a pressure sensor placed under the lateral foot and connected to a buzzer that elicited a noise when pressure exceeded the set threshold. Cues provided during the biofeedback conditions were used to promote proper biomechanics during each task.Main Outcome Measure(s)We measured the location of center-of-pressure (COP) data points during balance with eyes open and eyes closed for each condition. Plantar pressure in the lateral column of the foot during functional tasks was extracted. Secondary outcomes of interest were COP area and velocity, time to boundary during static balance, and additional plantar-pressure measures.ResultsBoth biofeedback conditions reduced COP in the anterolateral quadrant while increasing COP in the posteromedial quadrant of the foot during eyes-open balance. Visual biofeedback increased lateral heel pressure and the lateral heel and midfoot pressure-time integral during hops. The auditory condition produced similar changes during the eyes-closed trials. Auditory biofeedback increased heel pressure during step downs and decreased the lateral forefoot pressure-time integral during lunges.ConclusionsReal-time improvements in balance strategies were observed during both external biofeedback conditions. Visual and auditory biofeedback appeared to effectively moderate different functional-task biomechanics.     

Bilateral Improvements in Lower Extremity Function After Unilateral Balance Training in Individuals With Chronic Ankle Instability

Context:

Bilateral improvements in postural control have been reported among individuals with acute lateral ankle sprains and individuals with chronic ankle instability (CAI) when only the unstable ankle is rehabilitated. We do not know if training the stable ankle will improve function on the unstable side.

Objective:

To explore the effects of a unilateral balance-training program on bilateral lower extremity balance and function in individuals with CAI when only the stable limb is trained.

Design:

Cohort study.

Setting:

University clinical research laboratory.

Patients or Other Participants:

A total of 34 volunteers (8 men, 26 women; age = 24.32 ± 4.95 years, height = 167.01 ± 9.45 cm, mass = 77.54 ± 23.76 kg) with CAI were assigned to the rehabilitation (n = 17) or control (n = 17) group. Of those, 27 (13 rehabilitation group, 14 control group) completed the study.

Intervention(s):

Balance training twice weekly for 4 weeks.

Main Outcome Measure(s):

Foot and Ankle Disability Index (FADI), FADI Sport (FADI-S), Star Excursion Balance Test, and Balance Error Scoring System.

Results:

The rehabilitation and control groups differed in changes in FADI-S and Star Excursion Balance Test scores over time. Only the rehabilitation group improved in the FADI-S and in the posteromedial and anterior reaches of the Star Excursion Balance Test. Both groups demonstrated improvements in posterolateral reach; however, the rehabilitation group demonstrated greater improvement than the control group. When the groups were combined, participants reported improvements in FADI and FADI-S scores for the unstable ankle but not the stable ankle.

Conclusions:

Our data suggest training the stable ankle may result in improvements in balance and lower extremity function in the unstable ankle. This further supports the existence of a centrally mediated mechanism in the development of postural-control deficits after injury, as well as improved postural control after rehabilitation.Key Words: overflow, crossover training, rehabilitation

Key Points

• The rehabilitation group performed better over time on the Foot and Ankle Disability Index Sport and the Star Excursion Balance Test (SEBT) in the anterior, posteromedial, and posterolateral directions, but this was not dependent on ankle.
• Training the stable ankle may provide therapeutic benefit to the unstable ankle.
• Performance on the Balance Error Scoring System did not reflect a therapeutic benefit of the neuromuscular-control training program, but the result should be interpreted with caution.
• Clinicians should consider incorporating rehabilitation of the stable ankle in the overall plan for patients who may not be ready to initiate aspects of rehabilitation on the unstable ankle.

Lateral ankle sprain (LAS) is one of the most common injuries that athletes and recreationally active individuals sustain. Researchers have estimated that approximately 23 000 ankle sprains occur each day in the United States, equating to 1 sprain per 10 000 people.¹ As many as 33% to 42% of these injuries result in chronic ankle instability (CAI).^2,3 In the literature, CAI has been defined as the tendency of the ankle to “give way” during normal activity and can occur in the absence of mechanical instability.^4–6 One explanation for this tendency is that damage to the peripheral mechanoreceptors that provide proprioceptive input results in altered efferent modulation. Together, the changes in afferent input and efferent output are recognized as altered neuromuscular control (NMC). When specifically considering the role of NMC in facilitating joint stability, NMC has been defined as “the unconscious activation of dynamic restraints occurring in preparation for and in response to joint motion and loading.”⁷ Ultimately, altered NMC is thought to result in functional ankle instability.^3,4,8 Even after the injury has healed, mechanoreceptors may not function properly, resulting in NMC deficits that can lead to CAI.^3,8In addition to damage at the level of the receptors, changes in central nervous system processing and integration also may contribute to CAI.^9,10 Evidence has suggested that when an injury occurs, this central mechanism for NMC is disrupted.^9–12 Reports of bilateral postural-control deficits after acute LAS have provided further evidence that central pathways are affected by injury.^9,10,13 In addition, researchers^10,14–16 have found bilateral improvements in NMC and postural stability after rehabilitation of acute LAS and CAI. This suggests that NMC is not controlled solely by peripheral mechanoreceptors and that deficits after LAS may be partly due to adaptations in the central pathways. Whereas investigators^10,14–16 have shown a carryover effect after training the involved lower extremity, no one has examined whether training the stable ankle results in improvements to the unstable ankle.Given these reports of bilateral deficits after unilateral injury and improvements in NMC and postural stability in the stable ankle after training only the unstable ankle, it is conceivable that training the stable ankle in individuals with CAI would result in improvements of the unstable ankle. This is meaningful because clinicians may be able to begin neuromuscular retraining earlier and the athlete may be able to return to sport participation better prepared without increasing the time missed. After an acute LAS, many athletes return to sport participation within 15 days¹⁷ despite postural-control deficits being measured up to 21 days after injury⁹ and many reporting pain and functional deficits 6 months later.¹⁷ Researchers¹⁸ also have recommended that NMC training should not begin immediately because of pain and weight-bearing restrictions. Therefore, the amount of time spent restoring NMC before return to sport participation is minimal, likely resulting in athletes returning with residual dysfunction and increased risk for reinjury. By beginning NMC retraining sooner, it is plausible that athletes may return to sport participation with less dysfunction and more prepared for the functional demands of sport. Therefore, the purpose of our study was to explore the effects of a 4-week, unilateral balance-training program on bilateral lower extremity balance and function in individuals with CAI. Our hypothesis was that bilateral improvements would occur after training of the stable ankle.     

Clinical Examination Results in Individuals With Functional Ankle Instability and Ankle-Sprain Copers

Context:

Why some individuals with ankle sprains develop functional ankle instability and others do not (ie, copers) is unknown. Current understanding of the clinical profile of copers is limited.

Objective:

To contrast individuals with functional ankle instability (FAI), copers, and uninjured individuals on both self-reported variables and clinical examination findings.

Design:

Cross-sectional study.

Setting:

Sports medicine research laboratory.

Patients or Other Participants:

Participants consisted of 23 individuals with a history of 1 or more ankle sprains and at least 2 episodes of giving way in the past year (FAI: Cumberland Ankle Instability Tool [CAIT] score = 20.52 ± 2.94, episodes of giving way = 5.8 ± 8.4 per month), 23 individuals with a history of a single ankle sprain and no subsequent episodes of instability (copers: CAIT score = 27.74 ± 1.69), and 23 individuals with no history of ankle sprain and no instability (uninjured: CAIT score = 28.78 ± 1.78).

Intervention(s):

Self-reported disability was recorded using the CAIT and Foot and Ankle Ability Measure for Activities of Daily Living and for Sports. On clinical examination, ligamentous laxity and tenderness, range of motion (ROM), and pain at end ROM were recorded.

Main Outcome Measure(s):

Questionnaire scores for the CAIT, Foot and Ankle Ability Measure for Activities of Daily Living and for Sports, ankle inversion and anterior drawer laxity scores, pain with palpation of the lateral ligaments, ankle ROM, and pain at end ROM.

Results:

Individuals with FAI had greater self-reported disability for all measures (P < .05). On clinical examination, individuals with FAI were more likely to have greater talar tilt laxity, pain with inversion, and limited sagittal-plane ROM than copers (P < .05).

Conclusions:

Differences in both self-reported disability and clinical examination variables distinguished individuals with FAI from copers at least 1 year after injury. Whether the deficits could be detected immediately postinjury to prospectively identify potential copers is unknown.Key Words: laxity, chronic ankle instability, giving way, range of motion

Key Points

• Compared with copers, participants with functional ankle instability had greater self-reported disability, talar tilt laxity, and pain with inversion and limited sagittal-plane range of motion.
• Identifying dynamic coping mechanisms may help to improve ankle-sprain prevention and treatment strategies.

Functional ankle instability (FAI) is a common sequela of ankle sprain, affecting approximately 32% to 47% of patients with symptoms including sensations of giving way, subsequent sprains, and instability.^1–3 Because these symptoms can limit physical activity and activities of daily living for years after injury^2,3 and decrease quality of life,¹ significant resources have been dedicated to elucidating the mechanisms behind this condition. However, despite extensive research in this area, the factors that contribute to the development and continuation of FAI are still not clear.^4–6In the search to clarify current understanding, recent reports^7,8 have focused on ankle instability definitions and patient inclusion criteria. Delahunt et al⁷ highlighted the varied inclusion criteria in studies of chronic ankle instability and FAI. They emphasized that variability in the pathologic group may partially account for inconsistent findings in the research literature. In contrast to the highly variable FAI groups, the comparison groups in studies of ankle instability are very consistent. Comparison groups are generally individuals who have never sprained either ankle (the uninjured or control group).⁹ Some authors^10,11 have studied copers as an alternative comparison group: individuals with a history of lateral ankle sprain but no recurrent instability for at least 1 year postinjury. Rather than compare individuals with FAI with individuals who have never sprained an ankle, it may be more appropriate to compare them with individuals who have been exposed to the initial risk factor (lateral ankle sprain) but have not gone on to develop FAI.¹⁰ Although the precise mechanism of coping is still unknown,^11–14 insight into coping mechanisms may help explain why individuals with FAI are unable to cope after ankle sprain. Additionally, once identified, successful coping mechanisms may be useful in treating FAI.In recent years, a number of authors have included comparison groups of ankle-sprain copers.^11–14 Differences in functional performance,¹¹ self-assessed disability,^11–14 ligamentous laxity,¹² injury history,^11–13 lower extremity kinematics,¹⁴ ankle-joint stiffness,¹³ fibular position,¹³ and postural control^13,15 have been investigated. However, more information about the clinical profiles of these individuals is needed because it may help us to prospectively differentiate potential copers and noncopers (postsprain but before development of FAI). Clinicians could then target individuals who are likely to have recurrent injury, leading to more efficient use of resources and enhanced injury-prevention efforts. Such a prospective clinical screening evaluation already exists for patients with anterior cruciate ligament injuries.¹⁶ However, the ankle-instability literature is still several steps away from this type of measure.We believe one of the next steps to better understand ankle-sprain copers is to compile a profile of a typical coper, consisting of injury history, self-reported disability, and clinical examination and to compare that profile with the profiles of both individuals with FAI and uninjured individuals. Thus, the primary purpose of our study was to explore potential group (FAI, coper, and uninjured) differences in both self-reported variables (injury history and disability) and clinical examination variables (laxity, pain, and range of motion).     

Gait Kinematics After Taping in Participants With Chronic Ankle Instability

Context:

Chronic ankle instability is characterized by repetitive lateral ankle sprains. Prophylactic ankle taping is a common intervention used to reduce the risk of ankle sprains. However, little research has been conducted to evaluate the effect ankle taping has on gait kinematics.

Objective:

To investigate the effect of taping on ankle and knee kinematics during walking and jogging in participants with chronic ankle instability.

Design:

Controlled laboratory study.

Setting:

Motion analysis laboratory.

Patients or Participants:

A total of 15 individuals (8 men, 7 women; age = 26.9 ± 6.8 years, height = 171.7 ± 6.3 cm, mass = 73.5 ± 10.7 kg) with self-reported chronic ankle instability volunteered. They had an average of 5.3 ± 3.1 incidences of ankle sprain.

Intervention(s):

Participants walked and jogged in shoes on a treadmill while untaped and taped. The tape technique was a traditional preventive taping procedure. Conditions were randomized.

Main Outcome Measure(s):

Frontal-plane and sagittal-plane ankle and sagittal-plane knee kinematics were recorded throughout the entire gait cycle. Group means and 90% confidence intervals were calculated, plotted, and inspected for percentages of the gait cycle in which the confidence intervals did not overlap.

Results:

During walking, participants were less plantar flexed from 64% to 69% of the gait cycle (mean difference = 5.73° ± 0.54°) and less inverted from 51% to 61% (mean difference = 4.34° ± 0.65°) and 76% to 81% (mean difference = 5.55° ± 0.54°) of the gait cycle when taped. During jogging, participants were less dorsiflexed from 12% to 21% (mean difference = 4.91° ± 0.18°) and less inverted from 47% to 58% (mean difference = 6.52° ± 0.12°) of the gait cycle when taped. No sagittal-plane knee kinematic differences were found.

Conclusions:

In those with chronic ankle instability, taping resulted in a more neutral ankle position during walking and jogging in shoes on a treadmill. This change in foot positioning and the mechanical properties of the tape may explain the protective aspect of taping in preventing lateral ankle sprains.Key Words: external ankle supports, ankle prophylactic measures, recurrent ankle sprains

Key Points

• Taping the ankles of participants with chronic ankle instability resulted in more neutral positioning when they walked or jogged in shoes on a treadmill.
• Taping may protect the ankle by way of its mechanical properties and its neuromuscular effect on ankle position.

Lateral ankle sprains are very common injuries,¹ comprising an estimated 85% of all ankle injuries.^2,3 A history of ankle sprain has been found to be the leading risk factor in predicting future sprains.^4–6 Up to an estimated 70% of individuals who incur an initial ankle sprain and who are exposed to sports with a high risk of ankle-joint injuries will develop chronic ankle instability (CAI),^7,8 which is characterized by residual symptoms for at least 1 year after the initial ankle sprain.^8–10 Although the high prevalence of CAI is known, very little is actually understood regarding the mechanism or prevention of lateral ankle sprains.Gait kinematic alterations in those with a history of lateral ankle sprain have been hypothesized to contribute to CAI.^11–13 In a cadaver study¹⁴ of foot–floor clearance, inverting the foot 10°, regardless of plantar flexion, caused a collision between the lateral aspect of the foot and the floor, resulting in an ankle sprain. Individuals with CAI underestimate the combined motions of plantar flexion and inversion during passive joint position sense testing.¹⁵ These alterations in joint position sense may lead to alterations in kinematics during gait, which may contribute to ankle sprains and instability; an increased plantar-flexion touch-down position upon initial contact is known to increase the risk of ankle-joint injury.^14,16 Recently, researchers have compared the ankle kinematics of CAI participants with healthy controls while walking and jogging on a treadmill barefoot^17,18 and shod¹⁹ and walking on a walkway while shod.²⁰ Compared with healthy controls, frontal-plane and sagittal-plane kinematics were altered during various aspects of the gait cycle, and these changes are believed to contribute to repetitive incidences of ankle sprains.Prophylactic ankle taping is a common means of reducing the risk of injury to the lateral ankle ligaments, including recurrent ankle sprains.^21,22 The purpose of ankle taping is to restrict ankle inversion and plantar-flexion motion.^22,23 In healthy people, taping reduces sagittal-plane range of motion compared with the untaped condition while running, cutting, and landing from a drop.^24–26 Sagittal-plane kinematics during walking have been reported to be altered at foot contact and toe-off in individuals with CAI wearing an ankle brace.²⁷ During a functional drop landing, those with CAI demonstrated a decreased plantar-flexion angle immediately (50 milliseconds) before and at initial contact while wearing prophylactic ankle-joint taping compared with the untaped condition.²⁸ Previous researchers, however, have focused on discrete time points²⁷ or a specific window²⁸ during the gait cycle. We know of no literature evaluating frontal-plane and sagittal-plane kinematics during the entire walking and jogging gait cycle when CAI participants were taped.Therefore, the purpose of our study was to compare frontal-plane and sagittal-plane ankle kinematics in shod CAI participants while walking and jogging on a treadmill with or without traditional ankle taping. The secondary purpose was to evaluate sagittal-plane knee kinematics to determine if changes occurred with ankle taping. We evaluated kinematics at the knee to determine if kinematic alterations at the ankle affected movement up the kinetic chain.     

Balance Training and Center-of-Pressure Location in Participants With Chronic Ankle Instability

Context:Chronic ankle instability (CAI) occurs in some people after a lateral ankle sprain and often results in residual feelings of instability and episodes of the ankle''s giving way. Compared with healthy people, patients with CAI demonstrated poor postural control and used a more anteriorly and laterally positioned center of pressure (COP) during a single-limb static-balance task on a force plate. Balance training is an effective means of altering traditional COP measures; however, whether the overall location of the COP distribution under the foot also changes is unknown.Objective:To determine if the spatial locations of COP data points in participants with CAI change after a 4-week balance-training program.Design:Randomized controlled trial.Setting:Laboratory.Intervention(s):Participants were randomly assigned to a 4-week balance-training program or no balance training.Results:Overall, COP position in the balance-training group shifted from being more anterior to less anterior in both eyes-open trials (before trial = 319.1 ± 165.4, after trial = 160.5 ± 149.5; P = .006) and eyes-closed trials (before trial = 387.9 ± 123.8, after trial = 189.4 ± 102.9; P < .001). The COP for the group that did not perform balance training remained the same in the eyes-open trials (before trial = 214.1 ± 193.3, after trial = 230.0 ± 176.3; P = .54) and eyes-closed trials (before trial = 326.9 ± 134.3, after trial = 338.2 ± 126.1; P = .69).Conclusions:In participants with CAI, the balance-training program shifted the COP location from anterolateral to posterolateral. The program may have repaired some of the damaged sensorimotor system pathways, resulting in a more optimally functioning and less constrained system.Key Words: sprains, rehabilitation, postural control

Key Points

• A 4-week progressive balance-training program effectively altered the spatial locations of center-of-pressure data points in participants with chronic ankle instability.
• The alteration in the spatial locations of center-of-pressure data points may indicate a more optimally functioning sensorimotor system.

Lateral ankle ligament injuries are among the most common injuries in the general population, active-duty military service members, and athletes.^1–4 Although the initial symptoms associated with lateral ankle sprains generally resolve in a short time, many patients continue to report residual problems, such as pain, instability, and feelings of the ankle''s giving way.⁵ These residual symptoms have been reported to last 6 to 18 months after initial injury and have been observed in 55% to 72% of patients.^6–8 Repeated incidences of lateral ankle instability, recurrent sprains with persistent symptoms, and diminished self-reported function have been termed chronic ankle instability (CAI).^9,10Postural control requires integration of visual, vestibular, and somatosensory input.¹¹ Somatosensory input combines contributions from cutaneous, articular, and musculotendinous receptors. Afferent information gathered from these 3 sources is processed within the central nervous system and used to control motor commands.¹² Deficient contributions from any of the afferent receptors can lead to diminished postural control.^12–15 Postural-control deficits have been found repeatedly in patients with CAI.^9,10,16–26 These deficits have been identified using a variety of outcome measures, including time to stabilization,^18,22 Star Excursion Balance Test (SEBT) reach distances,¹⁹ center-of-pressure (COP) excursion measures, and time-to-boundary (TTB) measures.^23,27The COP measures from force-plate data can be analyzed to determine the instantaneous point of application of ground reaction forces, and they are useful in evaluating the stability and function of the foot.²⁸ Recently, Pope et al²⁷ evaluated a novel measure, COP location, which involves examining the location of COP data points in relation to the plantar aspect of the foot. Identifying the COP location indicates where the forces are distributed on the foot and provides insight into the postural-control strategy being used. Traditional COP measures and TTB measures cannot elicit the mechanism a person is using to improve balance. The COP location provides information about the spatial distributions of force application under the foot. To determine the COP location, the foot was modeled into a rectangle and divided into 16 equal sections. While the participant performed a single-limb balance task on a force plate, the location of each COP data point was mapped into 1 of the 16 sections. Differences were found between uninjured participants and those with CAI.²⁷ Specifically, COP was more anteriorly and laterally positioned in participants with CAI compared with uninjured persons during eyes-open and eyes-closed single-legged standing.²⁷ The authors hypothesized that this spatial difference may represent a more constrained sensorimotor system and compensatory postural-control mechanisms in participants with CAI.²⁷ Having a more anterolateral COP is likely associated with the foot being more supinated, placing the ankle and subtalar joints in a closed-packed and more stable position that decreases feelings of instability in those with CAI.²⁷ However, this positioning moves the COP closer to the lateral border of support and consequently decreases the amount of time available for postural corrections in this direction.²⁷ Plantar-pressure studies have also demonstrated increased force and pressure concentration under the lateral midfoot and forefoot in participants with CAI during gait, which supports the notion of an anterior and lateral COP shift.^29–31Balance-training programs have been effective in improving postural control in participants with CAI.^28,32–37 McKeon et al²⁸ showed static and dynamic postural-control improvements in a sample of participants with CAI after 4 weeks of balance training that was intended to challenge their sensorimotor systems. Significant improvement occurred in self-reported function, magnitude and variability of TTB measures, and SEBT reach distances compared with pretest and control values.²⁸Although balance improvements have been found after rehabilitation in those with CAI, the neuromechanical mechanism driving these changes is unknown. Determining how the COP location in patients with CAI is affected by a balance-training program may be useful beyond simply evaluating traditional COP measures and also provide insight into how to restore normal function. Understanding how a balance-training rehabilitation program changes COP location offers information on the adaptation strategies participants with CAI use and may enable clinicians to more specifically target each person''s deficits. The purpose of our study, therefore, was to determine how balance training affected COP location. We hypothesized that COP location would be more posteriorly and medially positioned, similar to that of the uninjured participants, after balance training.     

Physical Activity Levels in College Students With Chronic Ankle Instability

Context

Ankle sprains are the most common orthopaedic pathologic condition, and more concerning is the high percentage of persons who develop chronic ankle instability (CAI). Researchers have reported that patients with CAI are restricted occupationally, have more functional limitations, and have a poorer health-related quality of life. We do not know if these limitations decrease physical activity levels.

Objective

To assess total weekly steps taken between persons with CAI and persons with healthy ankles.

Design

Case-control study.

Setting

University research laboratory.

Patients or Other Participants

A total of 20 participants with unilateral CAI (9 men, 11 women; age = 21.2 ± 1.9 years, height = 174.3 ± 6.9 cm, mass = 71.9 ± 11.7 kg) and 20 healthy participants (9 men, 11 women; age = 20.4 ± 2.1 years, height = 172.1 ± 5.5 cm, mass = 73.1 ± 13.4 kg) volunteered.

Main Outcome Measure(s)

We provided all participants with a pedometer and instructed them to wear it every day for 7 days and to complete a daily step log. They also completed the Foot and Ankle Ability Measure (FAAM), the FAAM Sport version, and the International Physical Activity Questionnaire. A 2-way analysis of variance (group × sex) was used to determine if differences existed in the total number of weekly steps, ankle laxity, and answers on the International Physical Activity Questionnaire between groups and between sexes.

Results

We found no group × sex interaction for step count (F range = 0.439–2.108, P = .08). A main effect for group was observed (F_1,38 = 10.45, P = .04). The CAI group took fewer steps than the healthy group (P = .04). The average daily step count was 6694.47 ± 1603.35 for the CAI group and 8831.01 ± 1290.01 for the healthy group. The CAI group also scored lower on the FAAM (P = .01) and the FAAM Sport version (P = .01).

Conclusions

The decreased step count that the participants with CAI demonstrated is concerning. This decreased physical activity may be secondary to the functional limitations reported. If this decrease in physical activity level continues for an extended period, CAI may potentially be a substantial health risk if not treated appropriately.Key Words: ankle sprain, laxity, exercise

Key Points

• The chronic ankle instability (CAI) group was less physically active than the healthy group.
• Increased laxity in the CAI group may have contributed to differences in physical activity levels.
• The decreased step count in the CAI group may have been caused by increased joint laxity or by the corresponding changes in neuromuscular control that occur with joint instability.
• The long-term consequences of decreased physical activity with any musculoskeletal injury could lead to the development of chronic diseases and warrant further study.

Ankle sprains are the most common injury associated with physical activity.¹ Researchers² have reported recurrence rates after an initial ankle sprain as high as 70% and rates of developing chronic residual symptoms as high as 74%. The development of these residual symptoms, termed chronic ankle instability (CAI), has been linked directly to posttraumatic ankle osteoarthritis.³ Researchers have observed that participants with CAI have greater subjective disability,^4,5 neuromuscular changes,^6,7 and mechanical instability.^8–10 We do not know if these negative changes lead to decreased physical activity levels.Physical inactivity is classified as one of the 3 highest-risk behaviors in the development of cardiovascular disease; cancer; and other chronic diseases, such as diabetes and obesity.¹¹ Physical activity has been shown to protect against the development of osteoarthritis.¹² Thus, whereas often viewed as mild injuries, ankle sprains may represent a substantial public health problem and a major health care burden.¹³ The potential reduction in physical activity levels secondary to ankle pathologic conditions and the negative relationship that physical inactivity levels have on several chronic diseases is concerning.Investigators have consistently observed that participants with CAI score lower on subjective self-report scales, including the Foot and Ankle Ability Measure (FAAM), the Foot and Ankle Disability Index, and the Foot and Ankle Disability Index–Sport.^4,5,8–10 These questionnaires assess the participant''s ability to perform common activities of daily living (eg, walking, going up and down stairs). Investigators have reported that participants with ankle instability scored lower on health-related quality of life (HR-QOL) and had more functional limitations.¹⁴ In addition, a positive correlation was reported between HR-QOL scores and functional limitations. The HR-QOL addresses functioning in everyday life and personal evaluation of well-being.¹⁴ These decreases in subjective self-report and HR-QOL may negatively affect physical activity levels. If physical activity levels are decreased in patients with CAI, they could possibly have a negative effect on subjective function. However, we do not know the physical activity levels of persons with CAI and healthy persons or how physical inactivity, if present, is linked to changes in subjective function (Figure).Open in a separate windowFigure.Theoretical model showing how chronic ankle instability affects physical and functional impairments.Ankle laxity is an objective variable that influences subjective function. Increased laxity in persons with CAI has also been reported to relate to subjective function.⁵ If the ankle ligaments are not allowed to heal after an ankle sprain, subjective function may be negatively affected, which may affect physical activity levels. In a recent study from our laboratory,¹⁵ researchers demonstrated decreased physical activity levels in mice after an acute lateral ankle sprain. If this decreased physical activity continues across the life span, it could have numerous negative effects on overall health and well-being and, therefore, needs to be measured in patients with CAI. In addition, the differences in physical activity levels between males and females need to be examined. Researchers¹⁶ have observed a strong sex-related difference in physical activity levels. In the animal literature, investigators have reported that females are regularly more physically active than males, whereas authors of the human literature have suggested that males are more active than females.¹⁶ Further study is needed to examine if this difference exists with an injury model. Therefore, the purpose of our study was to assess total weekly steps taken between persons with CAI and persons with healthy ankles and between men and women in a university population. We also wanted to examine the relationship between ankle laxity and physical activity levels.     

Submaximal Force Steadiness and Accuracy in Patients With Chronic Ankle Instability

ContextPatients with chronic ankle instability (CAI) have demonstrated sensorimotor impairments. Submaximal force steadiness and accuracy measure sensory, motor, and visual function via a feedback mechanism, which helps researchers and clinicians comprehend the sensorimotor deficits associated with CAI.ObjectiveTo determine if participants with CAI experienced deficits in hip and ankle submaximal force steadiness and accuracy compared with healthy control participants.DesignCase-control study.SettingResearch laboratory.Patients or Other ParticipantsTwenty-one patients with CAI and 21 uninjured individuals.Main Outcome Measure(s)Maximal voluntary isometric contraction (MVIC) and force steadiness and accuracy (10% and 30% of MVIC) of the ankle evertors and invertors and hip abductors were assessed using the central 10 seconds (20%–87% of the total time) of the 3 trials.ResultsRelative to the control group, the CAI group demonstrated less accuracy of the invertors (P < .001). Across all motions, the CAI group showed less steadiness (P < .001) and less accuracy (P < .01) than the control group at 10% of MVIC. For MVIC, the CAI group displayed less force output in hip abduction than the uninjured group (P < .0001).ConclusionsPatients with CAI were unable to control ongoing fine force (10% and 30% of MVIC) through a feedback mechanism during an active test. These findings suggested that deficits in sensorimotor control predisposed patients with CAI to injury positions because they had difficulty integrating the peripheral information and correcting their movements in relation to visual information.     

Reliability and Sensitivity of the Foot and Ankle Disability Index in Subjects With Chronic Ankle Instability

Context: Despite the importance of patient's subjective reports of function, little research has addressed their use in the athletic population.Objective: To examine the following measurement properties of the Foot and Ankle Disability Index (FADI) and the FADI Sport: (1) intersession reliability during 1- and 6-week intervals, (2) sensitivity to differences between healthy subjects and subjects with chronic ankle instability (CAI), and (3) sensitivity to changes in function in those with CAI after rehabilitation.Design: Test-retest design.Setting: Laboratory setting.Patients or Other Participants: Fifty recreationally active subjects.Main Outcome Measure(s): FADI and FADI Sport.Results: Intraclass correlation coefficients (ICC 2,1) for the FADI and FADI Sport at 1 week were 0.89 and 0.84, respectively, for the involved limbs. Over 6 weeks, the ICC values for the involved limb of subjects who did not complete rehabilitation were 0.93 and 0.92, respectively. For both surveys, scores were significantly less for the involved limbs of subjects with CAI compared with their uninvolved limbs (P < .05). No significant side-to-side differences were noted among the healthy subjects. Scores on both surveys increased significantly after rehabilitation (FADI: P < .05, effect size = 0.52; FADI Sport: P < .05, effect size = 0.71).Conclusions: The FADI and FADI Sport appear to be (1) reliable in detecting functional limitations in subjects with CAI, (2) sensitive to differences between healthy subjects and subjects with CAI, and (3) responsive to improvements in function after rehabilitation in subjects with CAI.     

Muscle-Activation Onset Times With Shoes and Foot Orthoses in Participants With Chronic Ankle Instability

Context

Participants with chronic ankle instability (CAI) use an altered neuromuscular strategy to shift weight from double-legged to single-legged stance. Shoes and foot orthoses may influence these muscle-activation patterns.

Objective

To evaluate the influence of shoes and foot orthoses on onset times of lower extremity muscle activity in participants with CAI during the transition from double-legged to single-legged stance.

Design

Cross-sectional study.

Setting

Musculoskeletal laboratory.

Patients or Other Participants

A total of 15 people (9 men, 6 women; age = 21.8 ± 3.0 years, height = 177.7 ± 9.6 cm, mass = 72.0 ± 14.6 kg) who had CAI and wore foot orthoses were recruited.

Intervention(s)

A transition task from double-legged to single-legged stance was performed with eyes open and with eyes closed. Both limbs were tested in 4 experimental conditions: (1) barefoot (BF), (2) shoes only, (3) shoes with standard foot orthoses, and (4) shoes with custom foot orthoses (SCFO).

Main Outcome Measure(s)

The onset of activity of 9 lower extremity muscles was recorded using surface electromyography and a single force plate.

Results

Based on a full-factorial (condition, region, limb, vision) linear model for repeated measures, we found a condition effect (F_3,91.8 = 9.39, P < .001). Differences among experimental conditions did not depend on limb or vision condition. Based on a 2-way (condition, muscle) linear model within each region (ankle, knee, hip), earlier muscle-activation onset times were observed in the SCFO than in the BF condition for the peroneus longus (P < .001), tibialis anterior (P = .003), vastus medialis obliquus (P = .04), and vastus lateralis (P = .005). Furthermore, the peroneus longus was activated earlier in the shoes-only (P = .02) and shoes-with-standard-foot-orthoses (P = .03) conditions than in the BF condition. No differences were observed for the hip muscles.

Conclusions

Earlier onset of muscle activity was most apparent in the SCFO condition for ankle and knee muscles but not for hip muscles during the transition from double-legged to single-legged stance. These findings might help clinicians understand how shoes and foot orthoses can influence neuromuscular control in participants with CAI.Key Words: footwear, insoles, ankle sprains, neuromuscular system, electromyography

Key Points

• Shoes and foot orthoses accelerated muscle-activation onset times of the ankle and knee but not the hip in participants with chronic ankle instability.
• Earlier muscle-activation onset times were most prominent in the shoes-with-custom-foot-orthoses condition.
• At the ankle, the muscle-activation onset time of the peroneus longus was earlier in the shoes-only, shoes-with-standard-foot-orthoses, and shoes-with-custom-foot-orthoses conditions than in the barefoot condition, and the muscle-activation onset time of the tibialis anterior was earlier in the shoes-with-custom-foot-orthoses condition than in the barefoot condition.
• At the knee, the muscle-activation onset times of the vastus medialis obliquus and vastus lateralis were earlier in the shoes-with-custom-foot-orthoses condition than in the barefoot condition.
• The results may help clinicians understand how shoes and foot orthoses can influence neuromuscular control of the lower extremity in participants with chronic ankle instability.

Lateral ankle sprains are estimated to account for approximately 15% of all sport injuries.¹ Even more concerning than the initial ankle sprain is the large proportion of patients with residual symptoms and recurrent ankle sprains for months to years after the initial injury.² The occurrence of repetitive ankle sprains and the feeling of the ankle “giving way” with slight or no perturbation has been defined as chronic ankle instability (CAI).³The transition task from double-legged to single-legged stance during barefoot (BF) conditions has been shown to discriminate between uninjured participants and participants with CAI. Researchers have reported that muscle-activation onset times typically were delayed^4,5 and postural stability was impaired⁶ in participants with CAI, indicating the use of another strategy to shift weight from double-legged to single-legged stance. However, it is unclear whether findings from BF tests represent typical daily situations when shoes, and for some persons foot orthoses, are often worn.The human foot is the first point of contact between the body and a supporting surface. The cutaneous mechanoreceptors on the planar surface of the foot are an important source of sensory information,⁷ which is considered essential for achieving and maintaining functional joint stability.⁸ Shoes and foot orthoses act as an interface between the body and a supporting surface and can influence the sensory feedback from these mechanoreceptors by increasing the contact area between the foot and the supporting surface.^7,9 Furthermore, the small kinematic alterations of the rear foot and tibia that have been described with the use of shoes and foot orthoses¹⁰ may put the ankle joint in a more neutral position, thereby improving the capacity of the ankle mechanoreceptors to provide more accurate proprioceptive input toward the central nervous system.¹¹ Changing the sensory input to these mechanisms consequently would change the motor output.⁷Evidence is increasing that shoes and foot orthoses can influence lower extremity muscle activation.^10,12–14 Dingenen et al¹⁴ were the first investigators to measure the influence of shoes and foot orthoses on muscle-activation onset times of the entire lower extremity in uninjured participants during the transition from double-legged to single-legged stance. Their results showed that shoes and foot orthoses can accelerate muscle-activation onset times of the peroneus longus. No differences were reported in more proximal muscles. Recently, researchers have suggested that future investigators should be focused on the influence of shoes and foot orthoses on neuromuscular control, especially in participants with injuries, such as CAI,^10,13,14 to increase our understanding of how positive clinical outcomes from the use of shoes and foot orthoses can be achieved.¹¹ Altering or improving proprioceptive information and muscle-activation patterns in participants with CAI would be clinically beneficial, given that their proprioceptive and neuromuscular deficits have been described.¹⁵To our knowledge, no investigators have focused on the influence of shoes and foot orthoses on muscle-activation onset times of the entire lower extremity in participants with CAI during the transition from double-legged to single-legged stance. Therefore, the purpose of our study was to evaluate the influence of shoes and foot orthoses on muscle-activation onset times during the transition from double-legged to single-legged stance in participants with CAI. Based on the proposed effects of shoes and foot orthoses on lower extremity neuromuscular control, we hypothesized that shoes and foot orthoses would accelerate muscle-activation onset times compared with a BF condition.     

Alterations in Knee Kinematics and Dynamic Stability Associated With Chronic Ankle Instability

Context:

Chronic ankle instability (CAI) has been previously and separately associated with deficits in dynamic stability and proximal joint neuromuscular alterations, but how the 2 factors relate is unclear.

Objective:

To examine the contributions of lower extremity kinematics during an assessment of dynamic stability in participants with CAI.

Design:

Repeated-measures case-control design.

Setting:

Research laboratory.

Patients or Other Participants:

Thirty-eight volunteers were categorized into groups of those with unilateral CAI (10 men, 9 women; age  =  20.3 ± 2.9 years, height  =  1.77 ± 0.1 m, mass  =  76.19 ± 13.19 kg) and those without (10 men, 9 women; age  =  23.1 ± 3.9 years, height  =  1.72 ± 0.1 m, mass  =  72.67 ± 16.0 kg).

Intervention(s):

Participants performed 10 jump landings on each limb with a rest period between test limbs.

Main Outcome Measure(s):

Ankle plantar flexion, knee flexion, and hip flexion were captured with an electromagnetic tracking device at the point of ground impact. Ground reaction force data were used to calculate time to stabilization in the anteroposterior and mediolateral planes.

Results:

For the anteroposterior plane, we found a group-by-side interaction (P  =  .003), with the injured side of the CAI group demonstrating reduced dynamic stability. For knee flexion, a group main effect (P  =  .008) showed that the CAI group landed with less knee flexion than the control group.

Conclusions:

Diminished dynamic stability and decreased knee flexion angle at initial contact were apparent in the CAI group and may play a role in contributing to CAI. This altered kinematic pattern may influence preventive and therapeutic interventions for those with CAI.     

Lower Extremity Biomechanics in Athletes With Ankle Instability After a 6-Week Integrated Training Program

Context:

Plyometric exercise has been recommended to prevent lower limb injury, but its feasibility in and effects on those with functional ankle instability (FAI) are unclear.

Objective:

To investigate the effect of integrated plyometric and balance training in participants with FAI during a single-legged drop landing and single-legged standing position.

Design:

Randomized controlled clinical trial.

Setting:

University motion-analysis laboratory.

Patients or Other Participants:

Thirty athletes with FAI were divided into 3 groups: plyometric group (8 men, 2 women, age = 23.20 ± 2.82 years; 10 unstable ankles), plyometric-balance (integrated)–training group (8 men, 2 women, age = 23.80 ± 4.13 years; 10 unstable ankles), and control group (7 men, 3 women, age = 23.50 ± 3.00 years; 10 unstable ankles).

Intervention(s):

A 6-week plyometric-training program versus a 6-week integrated-training program.

Main Outcome Measure(s):

Postural sway during single-legged standing with eyes open and closed was measured before and after training. Kinematic data were recorded during medial and lateral single-legged drop landings after a 5-second single-legged stance.

Results:

Reduced postural sway in the medial-lateral direction and reduced sway area occurred in the plyometric- and integrated-training groups. Generally, the plyometric training and integrated training increased the maximum angles at the hip and knee in the sagittal plane, reduced the maximum angles at the hip and ankle in the frontal and transverse planes in the lateral drop landing, and reduced the time to stabilization for knee flexion in the medial drop landing.

Conclusions:

After 6 weeks of plyometric training or integrated training, individuals with FAI used a softer landing strategy during drop landings and decreased their postural sway during the single-legged stance. Plyometric training improved static and dynamic postural control and should be incorporated into rehabilitation programs for those with FAI.Key Words: plyometric training, balance training, landings, ankle injuries

Key Points

• After 6 weeks of isolated plyometric or combined plyometric and balance training, people with functional ankle instability demonstrated increased lower extremity maximal sagittal-plane angles and decreased maximal frontal-plane and transverse-plane angles on ground contact.
• Static and dynamic postural control improved with plyometric training, which should be included in rehabilitation programs for patients with functional ankle instability.

Ankle sprains often occur during physical activities such as basketball and soccer that require sudden stops, jumping, landing, and rotation around a planted foot. Although a patient with an ankle sprain may recover without experiencing persistent pain and swelling, most patients go on to develop chronic dysfunction, such as recurrent ankle sprain or instability.¹ Athletes report a 73% recurrence rate of lateral ankle sprain,² and the impairments associated with ankle sprain persist in 40% of patients 6 months after injury.³ These findings demonstrate that prolonged ankle dysfunction or disability is commonly attributable to ankle sprain.Functional ankle instability (FAI) is identified in those with symptoms such as frequent episodes of ankle giving way and feelings of ankle instability⁴ after ankle sprains and often presents with sensorimotor deficits in muscle reaction time, joint position sense, postural sway, and time to stabilization (TTS) of ground reaction force.^5,6 Several outcome measures, including center-of-pressure (COP) sway, leg reaching with the Star Excursion Balance Test, surface electromyography, and kinematics, are used to evaluate the neuromuscular and biomechanical characteristics of individuals with FAI. Measurement of COP sway during the single-legged stance is an easy way to evaluate static postural stability.⁷ People with ankle instability had greater variation in the magnitude of medial-lateral COP than a healthy group.⁸ In addition, TTS is effective for detecting differences between unstable and healthy groups.^9,10 The TTS for ground reaction force is the time required to achieve stability after a dynamic perturbation, and this time is longer in those with FAI.^9,11 In addition to TTS for ground reaction force, TTS for kinematics is a novel method to investigate the ability to regain balance in people with FAI; participants with FAI took longer TTS for ankle inversion after 1-legged hopping.¹² The advantage of using TTS for kinematics instead of TTS for ground reaction force is to provide more specific information about dynamic neuromuscular control of body segments.Rehabilitation programs for ankle sprain include muscle-strengthening, balance-training, neuromuscular-training, and proprioceptive-training protocols. The use of balance training for ankle reeducation has become common in recent years and is effective in reducing episodes of inversion.¹³ Balance training focuses on improving the ability to maintain a position through conscious and subconscious motor control.¹⁴ Certain tools, such as the balance board,¹⁵ Dura Disc, minitrampoline,¹⁶ biomechanical ankle platform system (BAPS),¹⁷ and Star Excursion Balance Test,¹⁸ can be used to assist training. In individuals with FAI, a 12-week BAPS exercise program with progressive testing reduced the radius of COP in single-legged standing.¹⁷ Another study¹⁹ showed that 4 weeks of balance improved shank-rearfoot coupling stability during walking. Proprioceptive training attempts to restore proprioceptive sensibility, retrain afferent pathways, and enhance the sensation of joint movement.¹⁴ Eils and Rosenbaum²⁰ found that 6 weeks of multi-station proprioceptive exercise in individuals with ankle instability reduced the standard deviation of COP (referring to the 68.2% range of COP dispersion) and maximum sway of COP (referring to the maximum range of COP dispersion) in the medial-lateral direction. However, Coughlan and Caulfield²¹ reported no change in ankle kinematics during treadmill walking and running after a 4-week neuromuscular training program with the “both sides up” (BOSU) balance trainer.Plyometric training has positive effects on sport performance, including distance running,²² jumping,²³ sprinting, and leg-extension force.²⁴ The focus of plyometric training is the stretch-shortening cycle induced in the muscle-tendon complex, where soft tissues repeatedly lengthen and shorten.²⁵ Plyometric exercise is described as “reactive neuromuscular training”²⁶ because it increases the excitability of the neurologic receptors and improves reactivity of the neuromuscular system. Plyometric training desensitizes the Golgi tendon organs through adaptation to the stretch-shortening exercise, which allows the elastic components of muscles to tolerate greater stretching.²⁷ Previously, plyometric training was theorized to improve neuromuscular control and dynamic stability, reduce the incidence of serious knee injuries,²⁸ and reduce the risk of injury by increasing functional joint stability of the lower limbs.^23,28 Furthermore, 6 weeks of plyometric exercise enhanced results on functional performance testing in athletes after lateral ankle sprain.²⁹ Plyometric exercise is thought to enable segments to absorb joint force effectively by promoting the mechanical advantage of soft tissue structures³⁰ through increasing initial and maximal knee and hip flexion during the jump-landing task.³⁰ The increased knee-flexion and hip-flexion angles during landing protect the knee via hamstrings tension.^31,32To date, investigations on the effect of plyometric training have emphasized functional performance^28,29 or preventing anterior cruciate ligament injuries.^33,34 Data on the feasibility and effectiveness of plyometric training in those with FAI are very limited.²⁹ Therefore, our purposes were to determine the effects on lower extremity biomechanics of a 6-week plyometric-training program or a 6-week integrated program with plyometric and balance training in athletes with FAI. We hypothesized that both training programs would increase maximum joint angles in the sagittal plane and reduce the time needed to regain stability during drop-landing tasks. We further hypothesized that the integrated training would reduce postural sway during single-legged stance and decrease the center of mass (COM)-COP deviation during drop-landing tasks.     

Differences in Lateral Drop Jumps From an Unknown Height Among Individuals With Functional Ankle Instability

Context:

Functional ankle instability (FAI) is a debilitating condition that has been reported to occur after 20% to 50% of all ankle sprains. Landing from a jump is one common mechanism of ankle injury, yet few researchers have explored the role of visual cues and anticipatory muscle contractions, which may influence ankle stability, in lateral jumping maneuvers.

Objective:

To examine muscle-activation strategies between FAI and stable ankles under a lateral load and to evaluate the differences in muscle activation in participants with FAI and participants with stable ankles when they were unable to anticipate the onset of lateral loads during eyes-open versus eyes-closed conditions.

Design:

Case-control study.

Setting:

Controlled laboratory setting.

Patients or Other Participants:

A total of 40 people participated: 20 with FAI and 20 healthy, uninjured, sex- and age-matched persons (control group).

Intervention(s):

Participants performed a 2-legged lateral jump off a platform onto a force plate set to heights of 35 cm or 50 cm and then immediately jumped for maximal height. They performed jumps in 2 conditions (eyes open, eyes closed) and were unaware of the jump height when their eyes were closed.

Main Outcome Measure(s):

Amplitude normalized electromyographic (EMG) area (%), peak (%), and time to peak in the tibialis anterior (TA), peroneus longus (PL), and lateral gastrocnemius (LG) muscles were measured.

Results:

Regardless of the eyes-open or eyes-closed condition, participants with FAI had less preparatory TA (t₁₅₈ = 2.22, P = .03) and PL (t₁₅₈ = 2.09, P = .04) EMG area and TA (t₁₅₈ = 2.45, P = .02) and PL (t₁₅₈ = 2.17, P = .03) peak EMG than control-group participants.

Conclusions:

By removing visual cues, unanticipated lateral joint loads occurred simultaneously with decreased muscle activity, which may reduce dynamic restraint capabilities in persons with FAI. Regardless of visual impairment and jump height, participants with FAI exhibited PL and TA inhibition, which may limit talonavicular stability and intensify lateral joint surface compression and pain.Key Words: electromyography, peroneus longus, tibialis anterior, neuromuscular control

Key Points

• Participants with functional ankle instability (FAI) had less preparatory electromyographic (EMG) area and less peak EMG amplitude in the peroneus longus and tibialis anterior compared to control participants.
• When landing from a lateral jump, participants with FAI exhibited muscle-activation strategies that were different from those of participants with stable ankles.
• Participants with FAI did not appropriately increase dynamic stability relative to the functional demands.
• Decreased activation in the peroneus longus and tibialis anterior before landing from unknown heights has important clinical applications because it may place persons with FAI at risk for further injury during athletic activities.

Ankle injuries are one of the most common injuries in athletes, and evidence suggests that the cause of injury may not always involve mechanical laxity but rather complex abnormalities within the sensorimotor system.^1–3Approximately 50% of the population with lateral sprains experiences functional ankle instability (FAI), which is a frequent and serious pathologic sequela.^4,5 These persons often present with sensations of the ankle “giving way” and sudden “rollover” events, which are characteristic of FAI.^1,3 Several factors contributing to FAI have been proposed to result from the failure of the dynamic restraint mechanism, such as deficits in kinesthetic awareness and balance, weakness of the musculature, mechanical laxity, and many other influences.^1,3,6–10 However, limited data are available to establish whether persons with FAI attempt to negotiate sensory conflicts with different dynamic restraint strategies when confronted with sudden lateral ankle loading during functional activities.¹¹Sudden bouts of instability to the ankle can occur during many functional tasks, including walking, running, cutting, and jumping.¹² During athletic competition, the combination of high-speed, ballistic-like movements and rapid joint loading requires people to use feed-forward motor control to execute preprogrammed movement strategies.¹³ Based on past experiences, the central nervous system develops and executes the preactivation strategies to anticipate the expected joint loads associated with specific maneuvers.^14,15 Preactivation of muscles is an important contributor to joint stability because properly tensioned muscles optimize joint stiffness for dynamic restraint and functional performance capabilities.^16–19 If somatosensory information is misinterpreted or incompatible with physical events, optimal stiffness may not be achieved, and both functional performance and joint stability may be compromised.Much of the previous research on muscle activation has focused on various types of forward or sagittal-plane movements (ie, forward gait, forward hopping, running).^7–11,13 In a study on gait, Caulfield and Garrett⁷ reported increased electromyographic (EMG) amplitude in the peroneus longus (PL) after heel strike among persons with FAI. In addition, decreased PL EMG amplitude has been observed before landing from a jump.^7,8 These differences in EMG activation of the PL may reflect compensatory strategies to dynamically protect the ankle joint from excessive inversion. In walking and forward-landing research, investigators^8,9,11,13 have provided some evidence of neuromuscular disparities in persons with FAI during activity. However, lateral maneuvers are also important functional tasks involved in the pathomechanics of injury and have not been measured adequately.Given that most athletic maneuvers are executed in multiplanar directions and that a combination of inversion and plantar flexion is a common contributor to ankle injury, researchers need to examine movements within other functional planes, such as lateral jumping.^3,20 Docherty et al²⁰ suggested that measurable functional performance deficits are present during lateral hopping in participants with instability, but no deficits are present when they are executing sagittal-plane functional movements. In earlier research, Delahunt et al¹¹ also demonstrated that participants with FAI have less eversion from 45 milliseconds before contact to 95 milliseconds after contact and have increased EMG activity in the tibialis anterior (TA) and soleus muscles during a lateral hop. These data show the differences of anticipatory muscle activation and joint positioning in preparation for joint loading and illustrate that participants with FAI may present with incorrect neuromuscular control strategies that could predispose them to future episodes of instability.In addition, increased EMG activity in the surrounding musculature has been seen with an increase in jump height.^15,21 Consequently, when a person knows there is a large drop-jump height, the amount of muscle stiffness increases to account for the increase in anticipated forces that will be placed on the ankle.^15,21 However, during physical activity, sensory conflict may occur and disrupt preparatory motor planning. If visual clues are lacking or conflicting, other input, such as proprioceptive and vestibular information, is necessary to modulate preactivation of muscles and navigate safe landings.¹⁵Muscle-activation strategies may be altered in patients with FAI and may influence dynamic restraint capabilities. It is not known whether persons with FAI execute normal preactivation strategies during lateral drop jumps or how they respond to conditions where they cannot anticipate the jump height. Potential differences in the preactivation of muscles in persons with FAI versus persons with stable ankles may provide insight about compensatory movement strategies underlying chronic sensations of the ankle giving way and instability. To our knowledge, no researchers have observed drop jumps with lateral loading of the ankle or have examined the effects of anticipatory muscle preactivation in FAI participants under unknown landing conditions. Therefore, the purpose of our research was 2-fold: (1) to examine muscle-activation strategies between persons with FAI and those with stable ankles under a lateral load and (2) to evaluate the differences in muscle activation in participants with FAI and participants with stable ankles when they were unable to anticipate the onset of lateral loads during eyes-open versus eyes-closed conditions.     

踝关节贴扎在优势侧落地动作中对膝关节生物力学特性的影响

目的 研究踝关节贴扎（限制踝关节内翻跖屈）在优势侧单腿落地动作中对膝关节生物力学特征的影响。方法 在踝关节未贴扎和贴扎两个条件下,18位业余运动员执行优势侧单腿落地动作,使用Vicon三维运动捕捉系统、Kistler测力台和Noraxon 表面肌电系统共同采集运动学、动力学、表面肌电数据,进行统计学分析。结果 与未贴扎相比,贴扎后触地时刻的膝关节屈曲角度和接触地面过程中膝关节最大屈曲角度显著性增加,而膝关节最大外翻角度显著性减小。结论 限制踝关节内翻跖屈贴扎可能会降低前交叉韧带损伤的风险。踝关节贴扎的干预方式能够改变在落地动作中膝关节生物力学指标。限制踝关节内翻跖屈贴扎可以作为预防大学生运动员前交叉韧带损伤的有效措施。     

Proprioception and Muscle Strength in Subjects With a History of Ankle Sprains and Chronic Instability

OBJECTIVE: To examine if patients with chronic ankle instability or a history of ankle sprains without chronic instability have worse proprioception or less invertor and evertor muscle strength. DESIGN AND SETTING: We assessed proprioception and muscle strength on the Biodex isokinetic dynamometer in the laboratory of the Department of Sports Medicine, University Hospital Ghent. SUBJECTS: Subjects included 87 physical education students (44 men, 43 women, age = 18.33 +/- 1.25 years, mass = 66.09 +/- 8.11 kg, height = 174.11 +/- 8.57 cm) at the University of Ghent in Belgium. Their ankles were divided into 4 groups: a symptom-free control group, subjects with chronic ankle instability, subjects who had sustained an ankle sprain in the last 2 years without instability, and subjects who sustained an ankle sprain 3 to 5 years earlier without instability. MEASUREMENTS: Active and passive joint-position sense was assessed at the ankle, and isokinetic peak torque was determined for concentric and eccentric eversion and inversion movements at the ankle. RESULTS: Statistical analysis indicated significantly less accurate active position sense for the instability group compared with the control group at a position close to maximal inversion. The instability group also showed a significantly lower relative eversion muscle strength (% body weight). No significant differences were observed between the control group and the groups with past sprains without instability. CONCLUSIONS: We suggest that the possible cause of chronic ankle instability is a combination of diminished proprioception and evertor muscle weakness. Therefore, we emphasize proprioception and strength training in the rehabilitation program for ankle instability.     

护踝对功能性踝关节不稳患者下肢运动生物力学特征的影响

目的 探究护踝对功能性踝关节不稳(functional ankle instability,FAI)患者的保护作用,为其护踝的选择提供依据。 方法 15 名 FAI 患者随机佩戴半刚性、弹性护踝及无护踝以自选速度步行和跑步,运用红外光点运动捕捉系统和三维测力台采集其下肢运动生物力学参数。 通过 3×2 重复设计的双因素方差分析检验护踝和运动模式对下肢运动学、动力学和能量吸收的影响。 结果 护踝与运动模式对本研究中所有指标均无交互作用(P>0. 05)。不论运动模式,与无护踝相比,弹性护踝显著减少了 FAI 患者踝关节内翻角峰值、内翻角速度和踝关节能量吸收(P<0. 05),同时增加了踝关节外翻力矩( P < 0. 001);而半刚性护踝增加了踝关节内翻角峰值和内翻角速度(P<0. 05)。 此外,弹性护踝可降低着地时刻的膝关节内旋力矩和外旋力矩峰值(P<0. 05)。 结论 与无护踝相比,弹性护踝通过减小踝关节内翻角、内翻角速度和能量吸收,增大踝关节外翻力矩,继而起到预防踝关节扭伤的作用。 FAI 患者佩戴半刚性护踝后需定时关注踝关节慢性损伤风险。 整体来看,弹性护踝的防护效果可能更有效,且未引起膝关节功能补偿,可作为预防 FAI 患者踝关节扭伤的有效措施。     

Ankle Dorsiflexion Among Healthy Men With Different Qualities of Lower Extremity Movement

Context:

Lower extremity movement patterns have been implicated as a risk factor for various knee disorders. Ankle-dorsiflexion (DF) range of motion (ROM) has previously been associated with a faulty movement pattern among healthy female participants.

Objective:

To determine the association between ankle DF ROM and the quality of lower extremity movement during the lateral step-down test among healthy male participants.

Design:

Cross-sectional study.

Setting:

Training facility of the Israel Defense Forces.

Patients or Other Participants:

Fifty-five healthy male Israeli military recruits (age = 19.7 ± 1.1 years, height = 175.4 ± 6.4 cm, mass = 72.0 ± 7.6 kg).

Intervention(s):

Dorsiflexion ROM was measured in weight-bearing and non–weight-bearing conditions using a fluid-filled inclinometer and a universal goniometer, respectively. Lower extremity movement pattern was assessed visually using the lateral step-down test and classified categorically as good or moderate. All measurements were performed bilaterally.

Main Outcome Measure(s):

Weight-bearing and non–weight-bearing DF ROM were more limited among participants with moderate quality of movement than in those with good quality of movement on the dominant side (P = .01 and P = .02 for weight-bearing and non–weight-bearing DF, respectively). Non–weight-bearing DF demonstrated a trend toward a decreased range among participants with moderate compared with participants with good quality of movement on the nondominant side (P = .03 [adjusted P = .025]). Weight-bearing DF was not different between participants with good and moderate movement patterns on the nondominant side (P = .10). Weight-bearing and non–weight-bearing ankle DF ROM correlated significantly with the quality of movement on both sides (P < .01 and P < .05 on the dominant and nondominant side, respectively).

Conclusions:

Ankle DF ROM was associated with quality of movement among healthy male participants. The association seemed weaker in males than in females.Key Words: anterior cruciate ligament, hip, knee, lateral step-down test, patellofemoral pain syndrome

Key Points

• Healthy males with a moderate quality of movement on the lateral step-down test exhibited less ankle-dorsiflexion range of motion than those with a good quality of movement.
• When a lower quality of movement is present in males, clinicians should consider interventions to increase ankle dorsiflexion.

An altered lower extremity movement pattern, consisting of excessive femoral adduction and internal rotation leading to excessive knee valgus alignment, has been implicated as a risk factor for patellofemoral pain syndrome (PFPS) and noncontact anterior cruciate ligament injuries.^1–3 Various factors have been suggested to contribute to an altered movement pattern, including decreased strength of the ipsilateral hip musculature,^4,5 increased subtalar joint pronation,^6,7 and altered motor control.⁸ Assessment of movement pattern and the factors associated with it is therefore commonly performed in the evaluation of patients with PFPS, as well as in screening for the risk of knee injury.^9–11Another possible contributor to an altered movement pattern is the available ipsilateral ankle-dorsiflexion (DF) range of motion (ROM). Decreased ankle DF ROM can limit the forward progression of the tibia over the talus during activities that require simultaneous knee flexion and ankle DF (eg, squatting, stair descent). A possible compensation for the limited motion of the tibia could be subtalar pronation, which may shift the tibia and the knee medially into greater valgus alignment.^6,12–14 Some evidence already exists for the association between ankle DF and the lower extremity movement pattern. Decreased DF has been previously associated with increased knee valgus during a drop-land maneuver,¹⁴ a squat,¹⁵ and a step-down maneuver¹⁶ among healthy participants.One limitation of the current literature regarding this topic is the inclusion of only female participants in many of the studies evaluating lower extremity movement patterns and the associated factors.^{4,6,14,16–18} This is likely because of sex differences in kinematics, kinetics, and muscle-activation patterns during various functional activities.^8,19,20 Women have been shown to perform activities such as cutting, jumping, and landing with greater knee valgus alignment and greater knee extension than men.^19,20 These differences are hypothesized to account for the greater incidence of noncontact anterior cruciate ligament tears and PFPS among women.^1,2,21,22 Accordingly, authors^14,16 of the 2 studies that have previously linked decreased ankle DF with a faulty movement pattern included only female participants as well. A third study of a mixed population demonstrated only a statistical trend for the association between ankle DF and a faulty movement pattern.¹⁵ It is therefore unclear whether the association between ankle DF and lower extremity movement pattern is similar for both sexes.Paradoxically, another limitation of the current literature is the use of sophisticated 3-D motion-analysis systems in many of the studies evaluating lower extremity movement patterns.^2,4,14,17,18 Although this type of analysis certainly contributes to a high level of precision and reliability, clinicians and coaches typically do not have the access, time, or skill to operate such systems. Instead, visual observation is often relied on to assess movement patterns in the clinic or on the field. It is unknown, however, to what extent any movement deviations identified during 3-D motion analyses correlate with movement deviations identified visually. Consequently, the findings from 3-D motion analyses studies may be difficult to apply in the clinical setting or on the field. We therefore decided to assess whether ankle DF ROM is related to the quality of lower extremity movement as assessed visually among healthy male participants.The lateral step-down (LSD) test is frequently used to assess movement patterns of the lower extremity.^9,11,23–25 Piva et al²⁵ suggested a visually based rating system for classifying the quality of movement during the LSD test. The reliability of this rating system has been established previously.^16,25 Our hypothesis was that male participants with a lower quality of movement on the LSD would exhibit less ankle DF ROM.