Core strength and lower extremity alignment during single leg squats

INTRODUCTION/PURPOSE: Muscles of the trunk, hip, and knee influence the orientation of the lower extremity during weight bearing activities. The purpose of this study was threefold: first, to compare the orientation of the lower extremity during a single leg (SL) squat among male and female athletes; second, to compare the strength of muscle groups in the trunk, hips, and knees between these individuals; and third, to evaluate the association between trunk, hip, and knee strength and the orientation of the knee joint during this activity. METHODS: Twenty-four male and 22 female athletes participated in this study. Peak isometric torque was determined for the following muscle actions: trunk flexion, extension, and lateral flexion, hip abduction and external rotation, and knee flexion and extension. The frontal plane projection angle (FPPA) of the knee during a 45 degrees SL squat was determined using photo editing software. RESULTS: Males and females moved in opposite directions during the SL squat test (F(1,42) = 5.05, P = 0.03). Females typically moved toward more extreme FPPA during SL squats (P = 0.056), while males tended to move toward more neutral alignment (P = 0.066). Females also generated less torque in all muscle groups, with the exception of trunk extension. The projection angle of the knee during the SL squat test was most closely associated with hip external rotation strength. CONCLUSION: Using instruments suitable for a clinical setting, females were found to have greater FPPA and generally decreased trunk, hip, and knee isometric torque. Hip external rotation strength was most closely associated with the frontal plane projection angle.     

Trunk,pelvis, and knee kinematics during running in females with and without patellofemoral pain

BackgroundFemales are two times more likely to develop patellofemoral pain (PFP) than males. Abnormal trunk and pelvis kinematics are thought to contribute to the pathomechanics of this condition. However, there is a scarcity of evidence investigating proximal segments kinematics in females with PFP.Research questionThe purpose of this study was to investigate whether females with PFP demonstrate altered trunk, pelvis, and knee joint kinematics compared with healthy controls during running.MethodsThirty-four females (17 PFP, 17 controls) underwent a 3-dimensional motion analysis during treadmill running at preferred and fixed speeds, each trial for 30 s. Variables of interest included magnitudes of peak angles for trunk (forward flexion, ipsilateral trunk lean), pelvis (anterior tilt, contralateral drop), knee (flexion, valgus, internal rotation), range of motion (RoM) of trunk and pelvis in sagittal and frontal planes and RoM of knee joint in the three cardinal planes of motion. Kinematic data were compared between groups using mixed model repeated measure analysis of variance with the trial as the repeated measure.ResultsThe PFP group displayed significantly less pelvis frontal plane RoM, greater knee frontal plane RoM, and less knee sagittal plane RoM during running compared with controls, irrespective of running trial. No differences were found in peak kinematic variables between PFP and healthy groups.SignificanceThese results may suggest a rigid stabilization strategy at the pelvis, which the body has adapted to prevent further frontal plane knee malalignment. Less knee sagittal plane RoM may be indicative of another protective strategy in the PFP group to avoid patellofemoral joint reaction force. Clinical assessments and rehabilitative treatments may benefit from considering a global program with focus on pelvis kinematics in addition to the knee joint in females with PFP.     

Relationship between passive ankle dorsiflexion range,dynamic ankle dorsiflexion range and lower limb and trunk kinematics during the single-leg squat

BackgroundLimited passive ankle dorsiflexion range has been associated with increased knee valgus during functional tasks. Increased knee valgus is considered a contributing factor for musculoskeletal disorders in the lower limb. There is conflicting evidence supporting this association. The extent of passive ankle dorsiflexion range is associated with dynamic ankle dorsiflexion range and the way how these variables are related to lower limb or trunk kinematics is unclear.Research questionWhat is the association between passive ankle dorsiflexion range or dynamic ankle dorsiflexion range with shank, thigh, pelvis or trunk movements during the single-leg squat?MethodsThis is a cross-sectional study with a convenience sample. Thirty uninjured participants performed the single-leg squat with their dominant limb. Ankle, shank, thigh, pelvis and trunk 3D kinematics were recorded. Passive ankle dorsiflexion range was assessed through the weight-bearing lunge test and the dynamic ankle dorsiflexion range was defined as the ankle dorsiflexion range of motion in the sagittal plane during the single-leg squat.ResultsGreater passive ankle dorsiflexion range was associated with smaller thigh internal rotation (r= -0.38). Greater dynamic ankle dorsiflexion range was associated with smaller trunk flexion (r = 0.59) and pelvis anteversion (r= -0.47). Passive ankle dorsiflexion range and dynamic ankle dorsiflexion range were not associated.SignificanceGreater passive ankle dorsiflexion range seems to be associated with a better lower limb alignment during the single-leg squat, while dynamic ankle dorsiflexion range seems to reflect different lower limb and trunk kinematic strategies.     

Reliability and validity of the Kinect V2 for the assessment of lower extremity rehabilitation exercises

BackgroundBesides its initial use as a video gaming system the Kinect might also be suitable to capture human movements in the clinical context. However, the system’s reliability and validity to capture rehabilitation exercises is unclear.Research questionThe purpose of this study was to evaluate the test-retest reliability of lower extremity kinematics during squat, hip abduction and lunge exercises captured by the Kinect and to evaluate the agreement to a reference 3D camera-based motion system.MethodsTwenty-one healthy individuals performed five repetitions of each lower limb exercise on two different days. Movements were simultaneously assessed by the Kinect and the reference 3D motion system. Joint angles and positions of the lower limb were calculated for sagittal and frontal plane. For the inter-session reliability and the agreement between the two systems standard error of measurement (SEM), bias with limits of agreement (LoA) and Pearson Correlation Coefficient (r) were calculated.ResultsParameters indicated varying reliability for the assessed joint angles and positions and decreasing reliability with increasing task complexity. Across all exercises, measurement deviations were shown especially for small movement amplitudes. Variability was acceptable for joint angles and positions during the squat, partially acceptable during the hip abduction and predominately inacceptable during the lunge. The agreement between systems was characterized by systematic errors. Overestimations by the Kinect were apparent for hip flexion during the squat and hip abduction/adduction during the hip abduction exercise as well as for the knee positions during the lunge. Knee and hip flexion during hip abduction and lunge were underestimated by the Kinect.SignificanceThe Kinect system can reliably assess lower limb joint angles and positions during simple exercises. The validity of the system is however restricted. An application in the field of early orthopedic rehabilitation without further development of post-processing techniques seems so far limited.     

Sex and limb differences during a single-leg cut with body borne load

BackgroundMilitary personnel don body borne loads that produce maladaptive lower limb biomechanics, increasing risk of musculoskeletal injury during common training tasks. Female personnel have over twice the injury risk as males, but it is unknown if a sex dimorphism in lower limb biomechanics exists during common training-related tasks.Research QuestionTo determine whether lower limb biomechanics exhibited during a single-leg cut with military body borne loads differ between sexes.MethodsSixteen females and 20 males had lower limb biomechanics quantified during five single-leg cuts off each limb with four loads (20, 25, 30 and 35 kg). Each cut required participants run 4 m/s, before planting their foot on a force platform and cut 45° towards the opposite limb. Lower limb biomechanics related to musculoskeletal injury were submitted to a repeated measures ANOVA to test for main and interaction effects of load, sex, and limb.ResultsDuring the cut, load increased peak proximal anterior tibial shear force (p < 0.001) and peak hip flexion (p = 0.010) and knee abduction (p = 0.045) moments, but decreased peak knee flexion angle (p = 0.032). Females exhibited greater peak proximal anterior tibial shear (p = 0.014), and peak hip adduction (p < 0.001) and knee external rotation (p = 0.001) moment than males. Dominant limb exhibited larger peak hip adduction (p = 0.002); whereas, the non-dominant limb exhibited greater peak hip internal (p = 0.002) and knee external (p = 0.007) rotation moments. Only the non-dominant limb increased peak knee abduction moment (p = 0.001) with additional load.SignificanceDuring the cut, adding body borne load produced maladaptive biomechanics that may increase knee musculoskeletal injury risk. Load increased peak proximal tibial shear and potential strain of knee’s soft-tissues. Females exhibited a sex dimorphism in lower limb biomechanics that may further elevate their injury risk. Both limbs exhibited biomechanics that may increase injury risk, but only the non-dominant limb further increased injury risk with load.     

Lower limb joint motion during a cross cutting movement differs in individuals with and without chronic ankle instability

ObjectiveTo compare the kinematics of lower limb joints between individuals with and without chronic ankle instability (CAI) during cross-turn and -cutting movements.DesignCross-sectional study.SettingMotion analysis laboratory.ParticipantsTwelve subjects with CAI and twelve healthy controls.Main outcome measuresHip flexion, adduction, and internal rotation, knee flexion, and ankle dorsiflexion and inversion angles were calculated in the 200 ms before initial ground contact and from initial ground contact to toe-off (stance phase) in a cross-turn movement during gait and a cross-cutting movement from a forward jump, and compared across the two groups.ResultsIn the cross-cutting movement, the CAI group exhibited greater hip and knee flexion than the control group during the stance phase, and more hip abduction during the period before initial contact and the stance phase. In the cross-turn movement the joint kinematics were similar in the two groups.ConclusionsCAI subjects exhibited an altered pattern of the proximal joint kinematics during a cross-cutting movement. It is important for clinicians to assess the function of the hip and knee as well as the ankle, and to incorporate coordination training for the entire lower limb into rehabilitation after lateral ankle sprains.     

A gait analysis of simulated knee flexion contracture to elucidate knee-spine syndrome

Knee flexion contracture influences the physiological movements in lower extremities and may cause the kinematic changes of the trunk. Our purpose was to investigate static and dynamic changes in trunk kinematics with simulated knee flexion contracture. Ten healthy females averaged 62 years participated in our study. Unilateral knee flexion contractures of 15° and 30° were simulated with a knee brace. Relaxed standing and level walking were measured at our laboratory using a motion analysis system which consisted of five cameras, a force plate, and thirteen retro-reflective markers. Three-dimensional trunk kinematics and vertical knee forces (% Body Weight) with the contractures were compared with those without the contracture. The 15° contracture did not significantly change trunk kinematics. However, the 30° contracture significantly changed the kinematics in each of the following planes. In the coronal plane, the trunk tilted to the contracture side in standing and walking. In the sagittal plane, posterior inclination of the pelvis in standing significantly increased. In addition, anterior inclination of the trunk and pelvis during walking significantly increased. In the axial plane, trunk rotation to the unaffected side significantly decreased during walking. The vertical knee force in the contracture limb decreased, being accompanied by the increase of the force in the unaffected limb during standing and walking. Results of our study suggest that knee flexion contracture significantly influences three-dimensional trunk kinematics during relaxed standing and level walking, and will lead to spinal imbalance. These facts may explain the onset of the “Knee-Spine Syndrome”.     

Fatigue matters: An intense 10 km run alters frontal and transverse plane joint kinematics in competitive and recreational adult runners

BackgroundFatigue is an essential component of distance running. Still, little is known about the effects of running induced fatigue on three-dimensional lower extremity joint movement, in particular in the frontal and transverse planes of motion.Research questionHow are non-sagittal plane lower extremity joint kinematics of runners altered during a 10 km treadmill run with near-maximum effort?MethodsIn a cross-sectional study design, we captured three-dimensional kinematics and kinetics at regular intervals throughout a 10 km treadmill run in 24 male participants (subdivided into a competitive and recreational runner group) at a speed corresponding to 105 % of their season-best time. We calculated average and peak joint angles at the hip, knee and ankle during the stance phase.ResultsWe observed peak deviations of 3.5°, 3° and 5° for the hip (more adduction), knee (more abduction) and ankle (more eversion) in the frontal plane when comparing the final (10 km) with the first (0 km) measurement. At the end of the run peak knee internal rotation angles increased significantly (up to 3° difference). Running with a more abducted knee joint and with a higher demand for hip abductor muscles in the unfatigued state was related to greater fatigue-induced changes of joint kinematics at the knee and hip.SignificanceThe fatigue related change of non-sagittal joint kinematics needs to be considered when addressing risk factors for running-related injuries, when designing shoe interventions as well as strengthening and gait retraining protocols for runners. We speculate that strengthening ankle invertors and hip abductors and monitoring the dynamic leg axis during running appear to be promising in preventing fatigue induced alterations of non-sagittal joint kinematics.     

Lower extremity kinematics and kinetics of Division III collegiate baseball and softball players while performing a modified pro-agility task

AIM: Females experience at least twice as many non-contact anterior cruciate ligament (ACL) injuries as males. The aim of this study was to investigate if males and females exhibited different characteristics while performing a modified pro-agility test. METHODS: Collegiate Division III male baseball (n=14) and female softball (n=13) players performed 4 trials of a modified pro-agility task, which consisted of running toward a force platform target for 5 steps, planting their right foot, and propelling themselves off of the target with their left foot. Kinematic and kinetic parameters were compared using a multivariate analysis of variance between gender with the level of significance set at P<0.05. RESULTS: Males and females exhibited similar knee valgus angles. Females had a greater maximum knee extension angle (10.14 degrees vs 17.43 degrees ), and greater knee range of motion (46.12 degrees vs 40.12 degrees ). Both groups reached maximum knee flexion at 52% of stance. Females had significantly more maximum hip flexion than males (28.86 degrees vs 22.75 degrees ). Females had significantly smaller minimum internal knee varus moments than their male counterparts (1.12 Nm/kg vs 1.55 Nm/kg). Vertical ground reaction forces as a percentage of bodyweight, and stance time, were not statistically different. The female group displayed an external knee rotation angle (2.49 degrees ) during the beginning of their stance, which was significantly different than the internal rotation angle (4.11 degrees ) in the male group. Early in stance knee rotation angle was highly correlated with the lack of internal knee varus moment (males R(2)=0.75, females R(2)=0.88). CONCLUSION: Females displayed knee moments and kinematics that may place them at greater risk for ACL injury during a stop-cut task. Females should be coached to perform stop cuts with more knee flexion and a more neutral knee rotation angle upon foot contact in an effort to reduce moments that may place the ACL at risk.     

The influence of task type and movement speed on lower limb kinematics during single-leg tasks

BackgroundSingle-leg squats and step-downs are commonly used to assess kinematic variables that may be linked to injuries. Task type and movement speed may influence the outcomes of interest because of different balance requirements.Research questionWhat is the influence of task type and movement speed on lower limb kinematics?MethodsThis is a cross-sectional within-subjects study where 22 physically active females performed three single-leg functional tasks (Squat, Anterior step-down, and Lateral step-down) at three movement speeds (slow [5 s], fast [2 s], and self-selected), while three-dimensional kinematic variables were recorded. Displacement values from the initial position in single-leg support until 60° or peak knee flexion were calculated. Two-way repeated measures ANOVA was used to compare tasks and speeds, and Cohen’s d effect size (ES) was calculated for significant pairwise comparisons.ResultsAt 60°, lateral step-down presented the greatest hip adduction (large ES) and internal rotation (small ES). The anterior step-down had the lowest knee abduction displacement while the squat had the greatest (small to medium ES). At peak knee flexion, values increased but differences between tasks followed a similar pattern. Slow speed induced smaller displacement angles at the knee and hip (trivial to small ES).SignificanceWhen knee abduction is the variable of interest, the SLS may be the best test since it elicits the greatest displacement, but when evaluating hip motion, SD_LAT might be best. Knee abduction and internal rotation were lowest in the slow condition, suggesting that faster speed may be more appropriate to detect abnormal movement patterns. However, the small difference in absolute values (i.e., degrees of movement) may indicate that the differences are not clinically significant, particularly for speed comparisons. Researchers and clinicians should take this into consideration when choosing the most appropriate task and the instruction to give during its execution.     

ACL-reconstructed and ACL-deficient individuals show differentiated trunk,hip, and knee kinematics during vertical hops more than 20 years post-injury

Purpose

Little is known regarding movement strategies in the long term following injury of the anterior cruciate ligament (ACL), and even less about comparisons of reconstructed and deficient knees in relation to healthy controls. The present purpose was to compare trunk, hip, and knee kinematics during a one-leg vertical hop (VH) ~20 years post-ACL injury between persons treated with surgery and physiotherapy (ACL_R), solely physiotherapy (ACL_PT), and controls (CTRL). Between-leg kinematic differences within groups were also investigated.

Methods

Sixty-six persons who suffered unilateral ACL injury on average 23 ± 2 years ago (32 ACL_R, 34 ACL_PT) and 33 controls performed the VH. Peak trunk, hip, and knee angles during Take-off and Landing phases recorded with a 3D motion capture system were analysed with multivariate statistics.

Results

Significant group effects during both Take-off and Landing were found, with ACL_PT differing from CTRL in Take-off with a combination of less knee flexion and knee internal rotation, and from both ACL_R and CTRL in Landing with less hip and knee flexion, knee internal rotation, and greater hip adduction. ACL_R also presented different kinematics to ACL_PT and CTRL in Take-off with a combination of greater trunk flexion, hip flexion, hip internal rotation, and less knee abduction, and in Landing with greater trunk flexion and hip internal rotation. Further, different kinematics and hop height were found between legs within groups in both Take-off and Landing for both ACL groups, but not for CTRL.

Conclusion

Different kinematics for the injured leg for both ACL groups compared to CTRL and between treatment groups, as well as between legs within treatment groups, indicate long-term consequences of injury. Compensatory mechanisms for knee protection seem to prevail over time irrespective of initial treatment, possibly increasing the risk of re-injury and triggering the development of osteoarthritis. Detailed investigation of movement strategies during the VH provides important information and a more comprehensive evaluation of knee function than merely hop height. More attention should also be given to the trunk and hip in clinics when evaluating movement strategies after ACL injury.

Level of evidence

Prospective cohort study, Level II.

     

Gender differences in the kinematics of unanticipated cutting in young athletes

PURPOSE: Anterior cruciate ligament (ACL) injuries occur at a greater rate in adolescent females compared with males who participate in the same pivoting and jumping sports. The purpose of this study was to compare knee and ankle joint angles between males and females during an unanticipated cutting maneuver. The hypotheses were that female athletes would display increased knee abduction, increased ankle eversion and decreased knee flexion during the unanticipated cutting maneuver compared with males. METHODS: Fifty-four male and 72 adolescent female middle and high school basketball players volunteered to participate in this study. Knee and ankle kinematics were calculated using three-dimensional motion analysis during a jump-stop unanticipated cut (JSUC) maneuver. RESULTS: Females exhibited greater knee abduction (valgus) angles compared with males. Gender differences were also found in maximum ankle eversion and maximum inversion during stance phase. No differences were found in knee flexion angles at initial contact or maximum. CONCLUSION: Gender differences in knee and ankle kinematics in the frontal plane during cutting may help explain the gender differences in ACL injury rates. Implementation of dynamic neuromuscular training in young athletes with a focus on frontal plane motion may help prevent ACL injuries and their long-term debilitating effects.     

Hip external rotation stiffness and midfoot passive mechanical resistance are associated with lower limb movement in the frontal and transverse planes during gait

BackgroundHip external rotation stiffness, midfoot passive mechanical resistance and foot alignment may influence on ankle, knee and hip movement in the frontal and transverse planes during gait.Research questionAre hip stiffness, midfoot mechanical resistance and foot alignment associated with ankle, knee and hip kinematics during gait?MethodsHip stiffness, midfoot mechanical resistance, and foot alignment of thirty healthy participants (18 females and 12 males) with average age of 25.4 years were measured. In addition, lower limb kinematic data during the stance phase of gait were collected with the Qualisys System (Oqus 7+). Stepwise multiple linear regressions were performed to identify if hip stiffness, midfoot torque, midfoot stiffness and foot alignment were associated with hip and knee movement in the transverse plane and ankle movement in the frontal plane with α = 0.05.ResultsReduced midfoot torque was associated with higher hip range of motion (ROM) in the transverse plane (r² = 0.18), reduced hip stiffness was associated with higher peak hip internal rotation (r² = 0.16) and higher ROM in the frontal plane (r² = 0.14), reduced midfoot stiffness was associated with higher peak knee internal rotation (r² = 0.14) and increased midfoot torque and midfoot stiffness were associated with higher peak knee external rotation (r² = 0.36).SignificanceThese findings demonstrated that individuals with reduced hip and midfoot stiffness have higher hip and knee internal rotation and higher ankle eversion during the stance phase of gait. On the other hand, individuals with increased midfoot torque and stiffness have higher knee external rotation. These relationships can be explained by the coupling between ankle movements in the frontal plane and knee and hip movements in the transverse plane. Finally, this study suggests that midfoot passive mechanical resistance and hip stiffness should be assessed in individuals presenting altered ankle, knee and hip movement during gait.     

Trunk flexion during walking in people with knee osteoarthritis

BackgroundOver 50% of the body’s mass is concentrated within the head, arms and trunk. Thus, small deviations in the orientation of the trunk, during normal walking, could influence the position of the centre of mass relative to the lower limb joint centres and impact on lower limb biomechanics. However, there are minimal data available on sagittal kinematics of the trunk in people with knee osteoarthritis (OA) during walking.Research questionDo people with knee OA have altered kinematic patterns of the trunk, pelvis or hip compared with healthy control participants during walking?MethodsStatistical parametric mapping was used to compare sagittal and frontal plane kinematic patterns, during walking, between a healthy group and cohort of people with knee OA.ResultsIndividuals with knee OA walked with a mean increase in trunk flexion of 2.6°. Although this difference was more pronounced during early stance, it was maintained across the whole of stance phase. There were no differences, between the groups, in sagittal plane pelvic or hip kinematics. There were also no differences in trunk, pelvic or hip kinematics in the frontal plane.SignificanceMost previous gait research investigating trunk motion in people with knee OA has focused on the frontal plane. However, our data suggest that an increase in sagittal trunk flexion may be a clinical hallmark of people with this disease. Altered trunk flexion could affect joint moments and muscle patterns and therefore our results motivate further research in this area.     

Effects of the use of oral contraceptives on hip and knee kinematics in healthy women during anterior stair descent

Purpose

Our aim was to evaluate the effects of the use of oral contraceptives (OC) on the hip and knee kinematics of healthy women during anterior stair descent.

Methods

Forty volunteers aged from 18 to 26 years were divided into two groups: 1—Group of women who had used OC for at least 3 months prior to evaluation (n = 20) and 2—Group of women who did not use OC (n = 20). The knee flexion/extension and abduction/adduction, hip flexion/extension, abduction/adduction and medial/lateral rotation excursions (degrees) were calculated for the dominant (supporting) limb during anterior stair descent. T tests for independent samples were used to compare the kinematic differences between the groups (α = 0.05).

Results

No significant difference was verified between the groups regarding the maximum excursion of knee flexion (n.s.) and abduction (n.s.) or hip flexion (n.s.), adduction (n.s.) and medial rotation (n.s.). When considering the knee flexion at 50°, no significant difference was verified between the groups regarding the excursion of knee abduction (n.s.) or hip flexion (n.s.) adduction (n.s.) and medial/lateral rotation (n.s.).

Conclusion

These results suggest that the use of OC does not influence the hip and knee kinematics during anterior stair descent. Therefore, the role of this medication as a protective factor against anterior cruciate ligament injuries remains questionable.

Level of evidence

III.     

Characteristic gait kinematics in persons with lumbosacral myelomeningocele

Thirty self-ambulatory children with mid-lumbar to low-sacral myelomeningocele who walked without aids and 21 control children were evaluated by three-dimensional gait analysis. Characteristic kinematic patterns and parameters in the trunk, pelvis, hip, knee and ankle were analyzed with respect to groups with successive weakness of the ankle plantarflexor, ankle dorsiflexor, hip abductor, hip extensor and knee flexor muscles. Extensive weakness of the plantarflexors resulted in kinematic alterations in the trunk, pelvis, hip and knee and in all three planes seen as knee flexion, anterior pelvic tilt and trunk and pelvic rotation. Additional extensive weakness of the dorsiflexors made little difference in the walking strategy. Large kinematic alterations in all planes were observed where there was a large extent of additional weakness of the hip abductor but strength remaining in the hip extensors. In this group, gait was characterized by large lateral sway of the trunk, rotation of the trunk and pelvis, pelvic hike and increased extension of the knees. In the group with total poresis hip extensors but yet some knee flexion, gait was similar to the previous group but there was less sagittal plane movement greates and posterior trunk tilt. Gait analysis provides an understanding of the compensatory strategies employed in these patients. Clinical management can be directed towards stabilizing the lower extremities and accommodating large upper body motion to preserve this method of self-ambulation even in children who have considerable hip extensor and abductor weakness.     

Sex differences in proximal control of the knee joint

Following the onset of maturation, female athletes have a significantly higher risk for anterior cruciate ligament (ACL) injury compared with male athletes. While multiple sex differences in lower-extremity neuromuscular control and biomechanics have been identified as potential risk factors for ACL injury in females, the majority of these studies have focused specifically on the knee joint. However, increasing evidence in the literature indicates that lumbo-pelvic (core) control may have a large effect on knee-joint control and injury risk. This review examines the published evidence on the contributions of the trunk and hip to knee-joint control. Specifically, the sex differences in potential proximal controllers of the knee as risk factors for ACL injury are identified and discussed. Sex differences in trunk and hip biomechanics have been identified in all planes of motion (sagittal, coronal and transverse). Essentially, female athletes show greater lateral trunk displacement, altered trunk and hip flexion angles, greater ranges of trunk motion, and increased hip adduction and internal rotation during sport manoeuvres, compared with their male counterparts. These differences may increase the risk of ACL injury among female athletes. Prevention programmes targeted towards trunk and hip neuromuscular control may decrease the risk for ACL injuries.     

The association between eccentric hip abduction strength and hip and knee angular movements in recreational male runners: An explorative study

Weak hip abductors may be related with increased hip adduction and knee abduction angular movement, which may be risk factors of lower extremity injuries. As the role of eccentric hip abduction strength (EHAS ) on hip adduction angular movement and knee abduction angular movement (KABD ) remains unclear, the purpose of this study was to explore the association between EHAS and hip and knee angular movement. In 100 healthy male recreational runners, EHAS was quantified using an isokinetic dynamometer, while hip and knee angular movements were collected using pressure‐sensitive treadmill and Codamotion active marker system. Using multiple linear regression models (n=186 legs), no relationships between EHAS and hip and knee kinematics were found. A possible reason for the lack of relationship between EHAS and hip and knee kinematics may be owing to differences in the running kinematics. Some runners with weak EHAS may compensate the weakness by leaning toward the stance limb and thereby reduces the demand on the hip abductors with the consequence of increased knee abduction moment, which may lead to an increased knee abduction angular excursion. Possible, others mechanism as the quadriceps strength and activity in the hip and thigh muscles may also be able to explain the lack of relationship that may or may not exist. Despite the inconclusive results of this study, the findings may suggest that weak hip abductor muscles may be a relevant factor to focus on in future studies.     

The effects of increased forward trunk lean during stair ascent on hip adduction and internal rotation in asymptomatic females

BackgroundIncreased hip adduction and internal rotation can lead to excessive patellofemoral joint stress and contribute to patellofemoral pain development. The gluteus maximus acts as a hip extensor, abductor, and external rotator. Improving hip extensor use by increasing one’s forward trunk lean in the sagittal plane may improve frontal and transverse plane hip kinematics during stair ascent.Research questionDoes increasing forward trunk lean during stair ascent affect peak hip adduction and internal rotation?MethodsTwenty asymptomatic females performed five stair ascent trials (96 steps/min) on an instrumented stair using their self-selected and forward trunk lean postures. Three-dimensional kinematics (200 Hz) and kinetics (2000 Hz) were recorded during the stance phase of stair ascent. Biomechanical dependent variables were calculated during the stance phase of stair ascent and included peak forward trunk lean, hip flexion, hip adduction, hip internal rotation angles, and the average hip extensor moment.ResultsDuring the forward trunk lean condition, decreases were observed for peak hip adduction (MD = 2.8˚; 95% CI = 1.9, 3.8; p < 0.001) and peak hip internal rotation (MD = 1.1˚; 95% CI = 0.1, 2.2; p = 0.04). In contrast, increases were observed during the forward trunk lean condition for the peak forward trunk lean angle (MD = −34.7˚; 95% CI = −39.1, −30.3; p < 0.001), average hip extensor moment (MD = −0.5 N·m/kg; 95% CI = −0.5, −0.4; p < 0.001), and stance time duration (MD = −0.02 s; 95% CI = −0.04, 0.00; p = 0.017).SignificanceIncreasing forward trunk lean and hip extensor use during stair ascent decreased peak hip adduction and internal rotation in asymptomatic females. Future studies should examine the effects of increasing forward trunk lean on hip kinematics, self-reported pain, and function in individuals with patellofemoral pain.     

Impact of fatigue on gender-based high-risk landing strategies

PURPOSE: Noncontact anterior cruciate ligament (ACL) injuries carry significant short- and long-term morbidity, particularly in females. To combat this epidemic, neuromuscular training has evolved aimed at modifying high-risk lower-limb biomechanics. However, injury rates and the gender disparity in these rates remain, suggesting that key components of the injury mechanism continue to be ignored. This study examined the potential contributions of neuromuscular fatigue to noncontact ACL injuries. METHODS: Ten male and 10 female NCAA athletes had 3D lower-limb-joint kinematics and kinetics recorded during 10 drop jumps, both before and after fatigue. Mean subject-based initial-contact (N = 9) and peak stance-phase kinematic (N = 9) and normalized (mass x height) kinetic (N = 9) parameters were quantified before and after fatigue and submitted to a three-way ANOVA to determine for the main effects of leg, gender, and fatigue. A Bonferroni corrected alpha level of 0.002 was adopted for all statistical comparisons. RESULTS: Females landed with more initial ankle plantar flexion and peak-stance ankle supination, knee abduction, and knee internal rotation compared with men. They also had larger knee adduction, abduction, and internal rotation, and smaller ankle dorsiflexion moments. Fatigue increased initial and peak knee abduction and internal rotation motions and peak knee internal rotation, adduction, and abduction moments, with the latter being more pronounced in females. CONCLUSIONS: Fatigue-induced modifications in lower-limb control may increase the risk of noncontact ACL injury during landings. Gender dimorphic abduction loading in the presence of fatigue also may explain the increased injury risk in women. Understanding fatigue effects at both the central and peripheral levels will further afford elucidation of the ACL injury mechanism and, hence, more successful prevention strategies.