Relationship of knee shear force and extensor moment on knee translations in females performing drop landings: a biplane fluoroscopy study

Background

Research has linked knee extensor moment and knee shear force to the non-contact anterior cruciate ligament injury during the landing motion. However, how these biomechanical performance factors relate to knee translations in vivo is not known as knee translations cannot be obtained with traditional motion capture techniques. The purpose of this study was to combine traditional motion capture with high-speed, biplane fluoroscopy imaging to determine relationships between knee extensor moment and knee shear force profiles with anterior and lateral tibial translations occurring during drop landing in female athletes.

Methods

15 females performed drop landings from a height of 40 cm while being recorded using a high speed, biplane fluoroscopy system and simultaneously being recorded using surface marker motion capture techniques to estimate knee joint angle, reaction force and moment profiles.

Findings

No significant statistical relationships were observed between peak anterior or posterior knee shear force and peak anterior and lateral tibial translations; or, between peak knee extensor moment and peak anterior and lateral tibial translations. Although differences were noted in peak shear force (P = 0.02) and peak knee extensor moment (P < 0.001) after stratification into low and high shear force and moment cohorts, no differences were noted in anterior and lateral tibial translations (all P ≥ 0.18).

Interpretation

Females exhibiting high knee extensor moment and knee shear force during drop landings do not yield correspondingly high anterior and lateral tibial translations.     

Sex comparison of hamstring structural and material properties

Background

Musculotendinous stiffness provides an estimate of resistance to joint perturbation, thus contributing to joint stability. Females demonstrate lesser hamstring stiffness than males, potentially contributing to the sex discrepancy in anterior cruciate ligament injury risk. However, it is unclear if the sex difference in hamstring stiffness is due to differences in muscle size or to inherent/material properties of the musculotendinous unit. It was hypothesized that hamstring stiffness, stress, strain, and elastic modulus would be greater in males than in females, and that hamstring stiffness would be positively correlated with muscle size.

Methods

Stiffness was assessed in 20 males and 20 females from the damping effect imposed by the hamstrings on oscillatory knee flexion/extension following joint perturbation. Hamstring length and change in length were estimated via motion capture, and hamstring cross-sectional area was estimated using ultrasound imaging. These characteristics were used to calculate hamstring material properties (i.e., stress, strain, and elastic modulus).

Findings

Stiffness was significantly greater in males than in females (P < 0.001). However, stress, strain, and elastic modulus did not differ across sex (P > 0.05). Stiffness was significantly correlated with cross-sectional area (r = 0.395, P = 0.039) and the linear combination of cross-sectional area and resting length (R² = 0.156, P = 0.043).

Interpretation

Male’s hamstrings possess a greater capacity for resisting changes in length imposed via joint perturbation from a structural perspective, but this property is similar across sex from a material perspective. Females demonstrate lesser hamstring stiffness compared to males in response to standardized loading conditions, indicating a compromised ability to resist changes in length associated with joint perturbation, and potentially contributing to the higher female ACL injury risk. However, the difference in hamstring stiffness is attributable in large part to differences in muscle size.     

Gluteal muscle activation during running in females with and without patellofemoral pain syndrome

Background

Hip and knee joint motion in the transverse and frontal plane during running may increase patellofemoral joint stress and contribute to the etiology of patellofemoral joint pain. We evaluated the association between these kinematics and the magnitude and timing of gluteus medius and maximus activity during running in females with patellofemoral pain. We also compared the magnitude and timing of gluteal muscle activity during running between females with and without patellofemoral pain.

Methods

Twenty females with patellofemoral pain and twenty females without knee pain participated in this study. Three-dimensional running kinematics, gluteus medius and gluteus maximus onset time, activation duration, mean activation level, and peak activation level were recorded simultaneously. Gluteal muscle timing and activation level were compared between groups using independent t-tests. The association of gluteal muscle activation parameters running kinematics in females with patellofemoral pain was quantified using Pearson correlation coefficients.

Findings

Females with patellofemoral pain demonstrated delayed (P = 0.028, effect size = 0.76) and shorter (P = 0.01, effect size = 0.88) gluteus medius activation than females without knee pain during running. The magnitude and timing of gluteus maximus activation was not different between groups. Greater hip adduction and internal rotation excursion was correlated with later gluteus medius and gluteus maximus onset, respectively.

Interpretation

Neuromuscular control differences of the gluteal muscles appear to exist among females with patellofemoral pain during running. Interventions to facilitate earlier activation of these muscles may be warranted among females with patellofemoral pain who demonstrate altered running kinematics.     

Neuromuscular alterations exist with knee osteoarthritis presence and severity despite walking velocity similarities

Background

Neuromuscular strategies during walking in individuals with knee osteoarthritis are being explored for diagnostic information; however, isolating differences to disease progression is difficult given walking velocity decreases with osteoarthritis severity. This study investigated lower extremity electromyograms during walking in asymptomatic individuals and individuals with different severities of knee osteoarthritis who walked with similar self-selected velocities.

Methods

Muscle activity in lateral and medial gastrocnemius, vastus lateralis and medialis, rectus femoris and the lateral and medial hamstrings was monitored during self-selected walking in 230 subjects with asymptomatic knees, moderate and severe knee osteoarthritis. Sixteen asymptomatic individuals, 16 individuals with moderate and 15 individuals with severe knee osteoarthritis were identified based on similarities in average walking velocity. Principal component analysis was employed to derive amplitude and temporal characteristics of the electromyographic (EMG) waveforms. Analysis of variance models tested for group and muscle differences in principal pattern scores (α = 0.05). Bonferroni post hoc testing was utilized on all significant findings.

Findings

Despite similar walking velocities, individuals with moderate knee OA had elevated and prolonged quadriceps and elevated lateral hamstring activity compared to asymptomatic individuals (P < 0.05). A diminished phase shift between medial and lateral gastrocnemius muscle activation, greater and prolonged lateral compared to medial hamstring activation were found in the severe group compared to asymptomatic and moderate knee OA groups (P < 0.05).

Interpretation

Lower extremity neuromuscular function during walking is altered with the presence and severity of knee osteoarthritis and not simply a direct function of walking velocity.     

Influences of hamstring stiffness and strength on anterior knee joint stability

Background

Excessive anterior tibial translation is a prospective risk factor for anterior cruciate ligament injury, thus factors which limit this motion may reduce injury risk. Stiffness quantifies a muscle's resistance to lengthening, and stiffer hamstrings may resist changes in length induced by anterior tibial translation more effectively.

Methods

Anterior tibial translation, hamstring strength, and hamstring stiffness were assessed in 30 physically active volunteers. Simple correlations were used to evaluate relationships between stiffness, strength, and anterior tibial translation. Anterior tibial translation data were arranged into high and low groups based on the median value, and hamstring strength and stiffness were compared between these groups via t-tests.

Findings

Anterior tibial translation was correlated with hamstring stiffness (r = −0.538; P = 0.002), but not with hamstring strength (r = −0.088; P = 0.644). Hamstring stiffness and strength were not correlated (r = 0.054; P = 0.778). Hamstring stiffness was greater in the low anterior tibial translation group (t₂₈ = 2.186; P < 0.037; ES = 0.36), but hamstring strength did not differ between these groups (t₂₈ = 1.057; P < 0.300; ES = 0.17).

Interpretation

Greater hamstring stiffness, but not strength, results in a more stable knee joint evidenced by less anterior tibial translation. These findings suggest that the hamstrings’ ability to resist lengthening rather than their overall force production capacity may be an important contributor to anterior cruciate ligament injury risk. As muscle stiffness can be modified acutely and chronically, enhancing hamstring stiffness may be an important addition to anterior cruciate ligament injury prevention programs.     

Differences in gait pattern parameters between medial and anterior knee pain in patients with osteoarthritis of the knee

Background

Patients with osteoarthritis of the knee have unique spatiotemporal gait alterations. These gait changes have not yet been differentiated according to the location of knee pain. The purpose of this study was to compare the gait patterns of patients with symptomatic knee osteoarthritis that exhibit either anterior or medial joint pain.

Methods

240 Patients with knee osteoarthritis were evaluated at one therapy center. Patients were divided into two groups according to the location of greatest pain in their worse knee. Patients underwent a computerized spatiotemporal gait analysis. Differences in gait patterns between the two knee pain locations were also examined within each gender.

Findings

Compared with patients with pain in the anterior knee compartment, those with pain in the medial knee compartment exhibited a significantly slower walking speed (P < 0.01), shorter step length (P < 0.01), lower single-limb-support phase (P < 0.01). These differences are witnessed mainly between the females in each group, whereas males differed only in single-limb-support.

Interpretation

The results of this study suggested underlying gait differences in the nature of medial and anterior knee pain. Furthermore, gender differences in gait may exist between patients with medial knee pain compared to patients with anterior knee pain.     

Are the kinematics of the knee joint altered during the loading response phase of gait in individuals with concurrent knee osteoarthritis and complaints of joint instability? A dynamic stereo X-ray study

Background

Joint instability has been suggested as a risk factor for knee osteoarthritis and a cause of significant functional decline in those with symptomatic disease. However, the relationship between altered knee joint mechanics and self-reports of instability in individuals with knee osteoarthritis remains unclear.

Methods

Fourteen subjects with knee osteoarthritis and complaints of joint instability and 12 control volunteers with no history of knee disease were recruited for this study. Dynamic stereo X-ray technology was used to assess the three-dimensional kinematics of the knee joint during the loading response phase of gait.

Findings

Individuals with concurrent knee osteoarthritis and joint instability demonstrated significantly reduced flexion and internal/external rotation knee motion excursions during the loading response phase of gait (P < 0.01), while the total abduction/adduction range of motion was increased (P < 0.05). In addition, the coronal and transverse plane alignment of the knee joint at initial contact was significantly different (P < 0.05) for individuals with concurrent knee osteoarthritis and joint instability. However, the anteroposterior and mediolateral tibiofemoral joint positions at initial contact and the corresponding total joint translations were similar between groups during the loading phase of gait.

Interpretations

The rotational patterns of tibiofemoral joint motion and joint alignments reported for individuals with concurrent knee osteoarthritis and joint instability are consistent with those previously established for individuals with knee osteoarthritis. Furthermore, the findings of similar translatory tibiofemoral motion between groups suggest that self-reports of episodic joint instability in individuals with knee osteoarthritis may not necessarily be associated with adaptive alterations in joint arthrokinematics.     

Lower limb muscle strengthening does not change frontal plane moments in women with knee osteoarthritis: A randomized controlled trial

Background

Osteoarthritis is a common musculo-skeletal problem accompanied with muscle weakness. Muscle weakness may be readily improved by resistance training. Greater muscle strength has been associated with a lower knee joint loading rate.

Methods

We conducted a single-blind randomized controlled trial of 54 female patients with osteoarthritis in at least one knee, according to the American College of Rheumatology clinical criteria. Patients were randomized into a 6-month high intensity progressive resistance training or a sham-exercise program. The primary outcomes were first peak knee and hip adduction moment measured using three-dimensional gait analysis at self-selected habitual and maximal speeds. Secondary outcomes were sagittal plane knee and hip moments, peak muscle strength, gait speed, and self-reported knee osteoarthritis symptoms measured by the Western Ontario and McMaster Osteoarthritis Index (WOMAC).

Findings

Six months of high intensity resistance training did not change the first peak knee or hip adduction moment at either habitual or maximum walking speeds (P > 0.413) compared to the sham-exercise. However, the second peak hip adduction moment (P = 0.025) and WOMAC pain score (P < 0.001) were reduced significantly in both groups over time, but there was no group effect. The changes in the second peak hip adduction moment were inversely related to the changes in the WOMAC pain score (r = − 0.394, P = 0.009).

Interpretations

Muscle strength training in women with osteoarthritis, while effective for reducing osteoarthritis symptoms, appeared to operate through mechanisms other than improved knee or hip joint loading, as paradoxically, improved symptoms were related to decreases of hip adduction moment in late stance.     

Biomechanical effects of joint line elevation in total knee arthroplasty

Background

Inadequate restoration of the knee joint line after total knee arthroplasty may lead to a poor clinical outcome. The purpose of this study was to quantitatively assess the effects of joint line elevation following total knee arthroplasty with increased joint volume on patellofemoral contact kinematics.

Methods

Six cadaveric specimens were tested. Patellofemoral contact area, contact pressure, and kinematics were measured following total knee arthroplasty with an anatomic joint line and after 4 and 8 mm of joint line elevation, at knee flexion angles of 0°, 30°, 60°, 90° and 120°. Repeated measures analysis of variance with a Tukey post hoc test with a significance level of 0.05 was used for statistical analyses.

Findings

There was a decrease in contact area with joint line elevation at flexion angles of 60°, 90° and 120° (P = 0.009–0.04). There was a significant increase in contact pressure only at 30° of knee flexion with 8 mm of joint line elevation (P = 0.004). Three of the six specimens showed inferior edge loading of the patella component following 8 mm of joint line elevation at 120° of knee flexion. The sagittal plane patellofemoral angle increased significantly with joint line elevation except for 0° knee flexion (P = 0.0002–0.02).

Interpretation

Knee joint line elevation with increased knee volume significantly affects patellofemoral contact area and kinematics and produced inferior edge loading/impingement between the patella and tibial components, this may result in loss of knee range of motion, postoperative pain, and premature component wear.     

Effect of an anterior-sloped brace joint on anterior tibial translation and axial tibial rotation: A motion analysis study

Background

Anterior tibial translation and axial tibial rotation are major biomechanical factors involved in anterior cruciate ligament injuries. This study sought to evaluate a brace prototype designed with an anterior-sloped joint, in terms of its efficacy in attenuating anterior tibial translation and axial tibial rotation during landing, using a motion analysis approach.

Methods

Ten healthy male subjects performed single-leg landing tasks from a 0.6-m height with and without the brace prototype. Ground reaction force and kinematics data were obtained using a motion-capture system and force-plates. Anterior tibial translation and axial tibial rotation were determined based on tibial and femoral marker reference frames. Vertical and anterior–posterior ground reaction forces, hip, knee and ankle joint range-of-motions and angular velocities, anterior tibial translation and axial tibial rotation were compared between unbraced and braced conditions using Wilcoxon signed-rank test.

Findings

We found no significant difference in peak vertical and anterior–posterior ground reaction forces (p = 0.770 and p = 0.332 respectively) between unbraced and braced conditions. Knee joint range-of-motion and angular velocity were lower (p = 0.037 and p = 0.038 respectively) for braced condition than unbraced condition. Anterior tibial translation and axial tibial rotation were reduced (p = 0.027 and p = 0.006 respectively) in braced condition, compared to unbraced condition.

Interpretation

The anterior-sloped brace joint helps to attenuate anterior tibial translation and axial tibial rotation present in the knee joint during landing. It is necessary to test the brace prototype in a sporting population with realistic sports landing situations in order to assess its effectiveness in lowering anterior cruciate ligament injury risk.     

Pre-operative muscle activation patterns during walking are associated with TKA tibial implant migration

Background

Gait biomechanical variables have been associated with total knee arthroplasty tibial implant migration measured with Radiostereometric Analysis (RSA), but no studies have examined the role of the periarticular musculature, which is responsible for a high proportion of the forces on the joint. The purpose of this study was to measure the pre-operative electromyography (EMG) patterns of the periarticular knee muscles during gait and determine the association of these patterns with the post-operative tibial implant migration measured with RSA. We hypothesized that pre-operative muscle activation patterns (specifically the activation patterns of the vastus and gastrocnemius muscle groups) measured with EMG are associated with migration at 6 months.

Methods

Electromyographic data were collected from 6 periarticular knee joint muscles on 37 patients pre-operatively during gait. Radiostereometric exams were performed immediately and at 6 months post-operatively. Relationships between the pre-operative patterns of muscle activation and micromotion of the implant were examined using Pearson correlation and regression models.

Findings

Statistically significant correlations were found between the pattern of the quadriceps and gastrocnemius muscle activations during gait and implant translation in the posterior direction. Regression analysis illustrated that a substantial proportion of the variance in the post-operative tibial component posterior translation (R2 = 0.49) was explained by a prolonged activation of the vastus medialis muscle and higher activation of the lateral gastrocnemius muscle during early stance.

Interpretation

The variability in migration explained by the muscle activation patterns supports the hypothesis that pre-operative functional characteristics can contribute to predicting implant migration following total knee arthroplasty surgery.     

Lower limb muscle pre-motor time measures during a choice reaction task associate with knee abduction loads during dynamic single leg landings

Background

Female neuromuscular control during dynamic landings is considered central to their increased ACL injury risk relative to males. There is limited insight, however, into the neuromuscular parameters governing this risk, which may hinder prevention success. This study targeted a new screenable and potentially trainable neuromuscular risk factor. Specifically, we examined whether lower limb muscle pre-motor times, being the time between stimulus presentation and initiation of the muscle EMG burst, elicited during a simple choice reaction task correlated with knee abduction loads during separate single leg landings.

Methods

Twenty female NCAA athletes had muscle (n = 8) pre-motor time and knee biomechanics data recorded bilaterally during a choice reaction task. Knee biomechanics were also quantified during anticipated and unanticipated single (dominant and non-dominant) leg landings. Mean peak knee abduction loads during landings were submitted to a two-way ANOVA to test for limb and decision effects. Individual regression coefficients were initially computed between-limb-based muscle pre-motor times and peak abduction moments elicited during both the choice reaction and landing tasks. Limb-based linear stepwise regression coefficients were also computed between muscle PMT's demonstrating significant (P < 0.05) individual associations and peak knee abduction moments during landings.

Findings

Peak knee abduction moments were significantly (P = 0.0001) larger during unanticipated (51.25 (7.41) Nm) compared to anticipated (38.93 (9.32) Nm) landings. Peak abduction moments were significantly (P < 0.05) correlated with bilateral medial gastrocnemius (r = 0.62 dominant; r = 0.63 non-dominant) and medial hamstring (r = 0.77 dominant; r = 0.79 non-dominant) pre-motor times elicited within the choice reaction task. Peak abduction moments during anticipated landings were significantly (P < 0.05) correlated with both dominant (r = 0.60) and non-dominant (r = 0.59) medial hamstring pre-motor times. For unanticipated landings, non-dominant and dominant peak knee abduction moments were significantly correlated with medial hamstring pre-motor time (r = 0.78) and combined medial gastroc and medial hamstring pre-motor times (r = 0.94) respectively.

Interpretation

Medial muscle pre-motor times during a specific choice reaction task are associated with peak knee abduction loads during separate single leg landings. These muscles appear critical in stabilizing the knee against the extreme dynamic load states associated with such tasks. Targeted screening and training of supraspinal processes governing these muscle pre-motor times may ultimately enable external knee loads associated with landings to be more effectively countered by the overarching neuromuscular strategy.     

Ageing modifies the fibre angle and biomechanical function of the lumbar extensor muscles

Background

Ageing is associated with geometrical changes in muscle fascicles that may lead to deteriorations in physical functions. The purpose of this study was to study the effects of ageing on fibre orientation and strength of the lumbar extensor muscles.

Methods

Fifty two healthy, 26 younger (10 males and 16 females, aged from 20 to 35) and 26 older (10 males and 16 females, aged from 65 to 90) volunteers participated in this study. Ultrasound images of the lumbar extensor muscles were obtained with the participants in relaxed standing and half flexion (50% of the range of trunk flexion). The fibre angles at the mid-substance of the muscle were recorded. Lumbar extensor muscle strength was measured in the upright posture with a load cell.

Findings

The mean lumbar extensor fibre angles were found to significantly decrease in the half flexion posture when compared to upright stance (P < 0.01). Both the fibre angle and the moment generation capability of the muscles decreased with ageing (P < 0.01). There was a moderate correlation between the fibre angles in the upright posture and the muscle strength measured in this posture (r = 0.40, P < 0.01).

Interpretation

Age-related changes in muscle geometry and posture may partly account for the deterioration in muscle function in the elderly.     

The impact of stochastic resonance electrical stimulation and knee sleeve on impulsive loading and muscle co-contraction during gait in knee osteoarthritis

Background

Increased impulsive loading and muscle co-contraction during gait have been observed in individuals with knee osteoarthritis. Proprioceptive deficits in this population may contribute to these effects. Proprioception has been shown to improve with the combination of stochastic resonance electrical stimulation and a knee sleeve in knee osteoarthritis. Our goal was to determine whether stochastic resonance stimulation combined with a knee sleeve would decrease impulsive loading rates and muscle co-contraction during gait in knee osteoarthritis.

Methods

Gait kinetics, kinematics and muscle activity were assessed during walking in subjects with knee osteoarthritis during three different conditions: no stochastic resonance/no sleeve (control), stochastic resonance at 75% threshold/sleeve, and no stochastic resonance/sleeve. Loading rates were calculated from the ground reaction force. Muscle co-contraction was calculated from the ratio of vastus lateralis to lateral hamstring activity. Differences between conditions were assessed using a repeated measures analysis of variance (P < 0.05).

Findings

The 75% threshold/sleeve and sleeve only conditions resulted in increased knee flexion at contact and reduced loading rates compared to the control condition (P < 0.05). However, these measures did not significantly differ between the 75% threshold/sleeve and sleeve only conditions. Muscle co-contraction was found to decrease with the 75% threshold/sleeve condition compared to the other conditions.

Interpretation

Increased knee flexion and decreased loading rates may be a result of proprioceptive improvements resulting from the sleeve or sleeve/stimulation combination. The stochastic resonance stimulation did not demonstrate an ability to enhance the effects of the sleeve with the exception of reductions in muscle co-contraction.     

Greater Q angle may not be a risk factor of patellofemoral pain syndrome

Background

A greater Q-angle has been suggested as a risk factor for Patellofemoral Pain Syndrome. Greater frontal plane knee moment and impulse have been found to play a functional role in the onset of Patellofemoral Pain Syndrome in a running population. Therefore, the purpose of this investigation was to determine the relationship between Q-angle and the magnitude of knee abduction moment and impulse during running.

Methods

Q-angle was statically measured, using a goniometer from three markers on the anterior superior iliac spine, the midpoint of the patella and the tibial tuberosity. Thirty-one recreational runners (21 males and 10 females) performed 8–10 trials running at 4 m/s (SD 0.2) on a 30 m-runway. Absolute and normalized knee moment and impulse were calculated and correlated with Q-angle.

Findings

Negative correlations between Q-angle and the magnitude of peak knee abduction moment (R² = 0.2444, R = − 0.4944, P = 0.005) and impulse (R² = 0.2563, R = − 0.5063, P = 0.004) were found. Additionally, negative correlations between Q-angle and the magnitude of weight normalized knee abduction moment (R² = 0.1842, R = − 0.4292, P = 0.016) and impulse (R² = 0.2304, R = − 0.4801, P = 0.006) were found.

Interpretation

The findings indicate that greater Q-angle, which is actually associated with decreased frontal plane knee abduction moment and impulse during running, may not be a risk factor of Patellofemoral Pain Syndrome.     

Effects of unloading bracing on knee and hip joints for patients with medial compartment knee osteoarthritis

Background

Osteoarthritis affects the whole body, thus biomechanical effects on other joints should be considered. Unloading knee braces could be effective for knee osteoarthritis, but their effects on the contralateral knee and bilateral hip joints remain unknown. This study investigated the effects of bracing on the kinematics and kinetics of involved and contralateral joints during gait.

Methods

Nineteen patients with medial compartment knee osteoarthritis were analysed. Kinematics and kinetics of the knee and hip joints in frontal and sagittal planes were measured during walking without and with bracing on the more symptomatic knee.

Findings

The ipsilateral hip in the braced condition showed a lower adduction angle by an average of 2.58° (range, 1.05°–4.16°) during 1%–49% of the stance phase, and a lower abduction moment at the second peak during the stance phase than the hip in the unbraced condition (P < 0.05 and P < 0.005, respectively). With bracing, the contralateral hip showed a more marked peak extension moment and lower abduction moment at the first peak (P < 0.05), and the contralateral knee adduction angle increased by an average of 0.32° (range, 0.21°–0.45°) during 46%–55% of the stance phase (P < 0.05), compared to no bracing.

Interpretation

Unloading bracing modified the contralateral knee adduction angle pattern at a specific time point during gait. It also affected the frontal plane on the ipsilateral hip and the frontal and sagittal planes on the contralateral hip joint. Consideration should be provided to other joints when treating knee osteoarthritis.     

Whole body, long-axis rotational training improves lower extremity neuromuscular control during single leg lateral drop landing and stabilization

Background

Poor neuromuscular control during sports activities is associated with non-contact lower extremity injuries. This study evaluated the efficacy of progressive resistance, whole body, long-axis rotational training to improve lower extremity neuromuscular control during a single leg lateral drop landing and stabilization.

Methods

Thirty-six healthy subjects were randomly assigned to either Training or Control groups. Electromyographic, ground reaction force, and kinematic data were collected from three pre-test, post-test trials. Independent sample t-tests with Bonferroni corrections for multiple comparisons were used to compare group mean change differences (P ≤ 0.05/21 ≤ 0.0023).

Findings

Training group gluteus maximus and gluteus medius neuromuscular efficiency improved 35.7% and 31.7%, respectively. Training group composite vertical–anteroposterior–mediolateral ground reaction force stabilization timing occurred 1.35 s earlier. Training group knee flexion angle at landing increased by 3.5°. Training group time period between the initial two peak frontal plane knee displacements following landing increased by 0.17 s. Training group peak hip and knee flexion velocity were 21.2°/s and 20.1°/s slower, respectively. Time period between the initial two peak frontal plane knee displacements following landing and peak hip flexion velocity mean change differences displayed a strong relationship in the Training group (r² = 0.77, P = 0.0001) suggesting improved dynamic frontal plane knee control as peak hip flexion velocity decreased.

Interpretation

This study identified electromyographic, kinematic, and ground reaction force evidence that device training improved lower extremity neuromuscular control during single leg lateral drop landing and stabilization. Further studies with other populations are indicated.     

Effects of repeated ankle stretching on calf muscle-tendon and ankle biomechanical properties in stroke survivors

Background

The objective of this study was to investigate changes in active and passive biomechanical properties of the calf muscle–tendon unit induced by controlled ankle stretching in stroke survivors.

Methods

Ten stroke survivors with ankle spasticity/contracture and ten healthy control subjects received intervention of 60-min ankle stretching. Joint biomechanical properties including resistance torque, stiffness and index of hysteresis were evaluated pre- and post-intervention. Achilles tendon length was measured using ultrasonography. The force output of the triceps surae muscles was characterized via the torque–angle relationship, by stimulating the calf muscles at a controlled intensity across different ankle positions.

Findings

Compared to healthy controls, the ankle position corresponding to the peak torque of the stroke survivors was shifted towards plantar flexion (P < 0.001). Stroke survivors showed significantly higher resistance torques and joint stiffness (P < 0.05), and these higher resistances were reduced significantly after the stretching intervention, especially in dorsiflexion (P = 0.013). Stretching significantly improved the force output of the impaired calf muscles in stroke survivors under matched stimulations (P < 0.05). Ankle range of motion was also increased by stretching (P < 0.001).

Interpretation

At the joint level, repeated stretching loosened the ankle joint with increased passive joint range of motion and decreased joint stiffness. At the muscle–tendon level, repeated stretching improved calf muscle force output, which might be associated with decreased muscle fascicle stiffness, increased fascicle length and shortening of the Achilles tendon. The study provided evidence of improvement in muscle tendon properties through stretching intervention.     

Effects of physiotherapy treatment on knee osteoarthritis gait data using principal component analysis

Background

Interpreting gait data is challenging due to intersubject variability observed in the gait pattern of both normal and pathological populations. The objective of this study was to investigate the impact of using principal component analysis for grouping knee osteoarthritis (OA) patients' gait data in more homogeneous groups when studying the effect of a physiotherapy treatment.

Methods

Three-dimensional (3D) knee kinematic and kinetic data were recorded during the gait of 29 participants diagnosed with knee OA before and after they received 12 weeks of physiotherapy treatment. Principal component analysis was applied to extract groups of knee flexion/extension, adduction/abduction and internal/external rotation angle and moment data. The treatment's effect on parameters of interest was assessed using paired t-tests performed before and after grouping the knee kinematic data.

Findings

Increased quadriceps and hamstring strength was observed following treatment (P < 0.05). Except for the knee flexion/extension angle, two different groups (G₁ and G₂) were extracted from the angle and moment data. When pre- and post-treatment analyses were performed considering the groups, participants exhibiting a G₂ knee moment pattern demonstrated a greater first peak flexion moment, lower adduction moment impulse and smaller rotation angle range post-treatment (P < 0.05). When pre- and post-treatment comparisons were performed without grouping, the data showed no treatment effect.

Interpretation

The results of the present study suggest that the effect of physiotherapy on gait mechanics of knee osteoarthritis patients may be masked or underestimated if kinematic data are not separated into more homogeneous groups when performing pre- and post-treatment comparisons.     

Comfort and midfoot mobility rather than orthosis hardness or contouring influence their immediate effects on lower limb function in patients with anterior knee pain

Background

Despite evidence for use of foot orthoses in the treatment of anterior knee pain, there is a paucity of research into their mechanisms of action. This study (i) determined the immediate lower limb kinematics and muscle activity adaptations, and (ii) evaluated the effect of individual's comfort and foot mobility.

Methods

Forty individuals diagnosed with anterior knee pain were measured for lower limb kinematics and electromyographic activity (via surface electrodes) while they jogged in three prefabricated contoured orthoses (hard, medium and soft) and a soft-flat orthosis. Subjects ranked orthoses in order of comfort.

Findings

Soft orthoses were more comfortable. No immediate adaptations in kinematics and electromyographic activity were observed when orthoses were added to shoes. There were few effects of perceived comfort and foot mobility, one being a significant interaction in frontal plane hip motion (Pillai's V = 0.089, P = 0.031) with the least comfortable orthosis producing the greatest relative adduction in those with mobile feet (0.54° (standard deviation 0.87)). Other main effects were a significant increase in vastus lateralis activity when wearing the least comfortable orthosis (6.94%, P = 0.007) and a delay in offset of medial gastrocnemius in individuals with less mobile feet (1.51%, P = 0.045).

Interpretation

It is becoming apparent that it is important to use more comfortable foot orthoses in a condition like anterior knee pain, where there is an associated increased hip adduction and vastus lateralis activity with least comfortable orthoses. Future research is needed to determine adaptations after ongoing wearing of orthoses.