Changes in foot progression angle during gait reduce the knee adduction moment and do not increase hip moments in individuals with knee osteoarthritis

People with knee osteoarthritis who adopt a modified foot progression angle (FPA) during gait often benefit from a reduction in the knee adduction moment and knee pain. It is unknown, however, whether changes in the FPA increase hip moments, a surrogate measure of hip loading, which may increase the risk of hip pain or osteoarthritis. This study examined how altering the FPA affects hip moments. Individuals with knee osteoarthritis walked on an instrumented treadmill with their baseline gait, 10° toe-in gait, and 10° toe-out gait. A musculoskeletal modeling package was used to compute joint moments from the experimental data. Fifty participants were selected from a larger study who reduced their peak knee adduction moment with a modified FPA. In this group, participants reduced the first peak of the knee adduction moment by 7.6% with 10° toe-in gait and reduced the second peak by 11.0% with 10 ° toe-out gait. Modifying the FPA reduced the early-stance hip abduction moment, at the time of peak hip contact force, by 4.3% ± 1.3% for 10° toe-in gait (p=0.005) and by 4.6% ± 1.1% for 10° toe-out gait (p<0.001) without increasing the flexion and internal rotation moments (p>0.15). In summary, when adopting a FPA modification that reduced the knee adduction moment, participants did not increase surrogate measures of hip loading.

Effects of Deficits in the Neuromuscular and Mechanical Properties of the Quadriceps and Hamstrings on Single-Leg Hop Performance and Dynamic Knee Stability in Patients After Anterior Cruciate Ligament Reconstruction

Background: Understanding the role of neuromuscular and mechanical muscle properties in knee functional performance and dynamic knee stability after anterior cruciate ligament reconstruction (ACLR) may help in the development of more focused rehabilitation programs. Purpose: To compare the involved and uninvolved limbs of patients after ACLR in terms of muscle strength, passive muscle stiffness, muscle activation of the quadriceps and hamstrings, hop performance, and dynamic knee stability and to investigate the association of neuromuscular and mechanical muscle properties with hop performance and dynamic knee stability. Study Design: Cross-sectional study; Level of evidence, 3. Method: The authors studied the quadriceps and hamstring muscles in 30 male patients (mean ± SD age, 25.4 ± 4.1 years) who had undergone unilateral ACLR. Muscle strength was measured using isokinetic testing at 60 and 180 deg/s. Passive muscle stiffness was quantified using ultrasound shear wave elastography. Muscle activation was evaluated via electromyographic (EMG) activity. Hop performance was evaluated via a single-leg hop test, and dynamic knee stability was evaluated via 3-dimensional knee movements during the landing phase of the hop test. Results: Compared with the uninvolved limb, the involved limb exhibited decreased peak torque and shear modulus in both the quadriceps and hamstrings as well as delayed activity onset in the quadriceps ( P < .05 for all). The involved limb also exhibited a shorter hop distance and decreased peak knee flexion angle during landing ( P < .05 for both). Decreased peak quadriceps torque at 180 deg/s, the shear modulus of the semitendinosus, and the reactive EMG activity amplitude of the semimembranosus were all associated with shorter hop distance ( R 2 = 0.565; P < .001). Decreased quadriceps peak torque at 60 deg/s and shear modulus of the vastus medialis were both associated with smaller peak knee flexion angle ( R 2 = 0.319; P < .001). Conclusion: In addition to muscle strength deficits, deficits in passive muscle stiffness and muscle activation of the quadriceps and hamstrings were important contributors to poor single-leg hop performance and dynamic knee stability during landing. Further investigations should include a rehabilitation program that normalizes muscle stiffness and activation patterns during landing, thus improving knee functional performance and dynamic knee stability.

Biomechanical Analysis of Running in Shoes with Different Heel-to-Toe Drops

The heel-to-toe drop of running shoes is a key parameter influencing lower extremity kinematics during running. Previous studies testing running shoes with lower or larger drops generally used minimalist or maximalist shoes, where the factors outside of the drop may lead to the observed changes in running biomechanics. Therefore, our aim was to compare the strike patterns, impact force, and lower extremity biomechanics when running in shoes that varied only in their drops. Eighteen habitual rearfoot strikers performed trials wearing running shoes with four drop conditions: 15 mm, 10 mm, 5 mm, and without a drop. Three-dimensional (3D) tracks of the reflective markers and impact force were synchronously collected using a video graphic acquisition system and two force plates. The biomechanical parameters were compared among the four drop conditions using one-way ANOVA of repeated measures. A greater foot inclination angle (p = 0.001, ηp2 = 0.36) at initial contact and a lower vertical loading rate (p = 0.002, ηp2 = 0.32) during the standing phase were found when running in shoes with large drops compared with running in shoes without a drop. Running in shoes with large drops, as opposed to without, significantly increased the peak knee extension moment (p = 0.002, ηp2 = 0.27), but decreased the peak ankle eversion moment (p = 0.001, ηp2 = 0.35). These findings suggest that the heel-to-toe drop of running shoes significantly influences the running pattern and the loading on lower extremity joints. Running shoes with large drops may be disadvantageous for runners with knee weakness and advantageous for runners with ankle weakness.

Modelling and identification of characteristic kinematic features preceding freezing of gait with convolutional neural networks and layer-wise relevance propagation

Background Although deep neural networks (DNNs) are showing state of the art performance in clinical gait analysis, they are considered to be black-box algorithms. In other words, there is a lack of direct understanding of a DNN’s ability to identify relevant features, hindering clinical acceptance. Interpretability methods have been developed to ameliorate this concern by providing a way to explain DNN predictions. Methods This paper proposes the use of an interpretability method to explain DNN decisions for classifying the movement that precedes freezing of gait (FOG), one of the most debilitating symptoms of Parkinson’s disease (PD). The proposed two-stage pipeline consists of (1) a convolutional neural network (CNN) to model the reduction of movement present before a FOG episode, and (2) layer-wise relevance propagation (LRP) to visualize the underlying features that the CNN perceives as important to model the pathology. The CNN was trained with the sagittal plane kinematics from a motion capture dataset of fourteen PD patients with FOG. The robustness of the model predictions and learned features was further assessed on fourteen PD patients without FOG and fourteen age-matched healthy controls. Results The CNN proved highly accurate in modelling the movement that precedes FOG, with 86.8% of the strides being correctly identified. However, the CNN model was unable to model the movement for one of the seven patients that froze during the protocol. The LRP interpretability case study shows that (1) the kinematic features perceived as most relevant by the CNN are the reduced peak knee flexion and the fixed ankle dorsiflexion during the swing phase, (2) very little relevance for FOG is observed in the PD patients without FOG and the healthy control subjects, and (3) the poor predictive performance of one subject is attributed to the patient’s unique and severely flexed gait signature. Conclusions The proposed pipeline can aid clinicians in explaining DNN decisions in clinical gait analysis and aid machine learning practitioners in assessing the generalization of their models by ensuring that the predictions are based on meaningful kinematic features.

On the hindlimb biomechanics of the avian take-off leap

Although extant land birds take to the air by leaping, generating the initial take-off velocity primarily from the hindlimbs, the detailed musculoskeletal mechanics remain largely unknown. We therefore simulated in silico the take-off leap of the zebra finch, Taeniopygia guttata, a model species of passerine, a class of bird which includes over half of all extant bird species. A 3D computational musculoskeletal model of the zebra finch hindlimb, comprising of 43 musculotendon units was developed and driven with previously published take-off ground reaction forces and kinematics. Using inverse dynamics, the external moments at the ankle, knee, and hip joints were calculated and contrasted to the cumulative muscle capability to balance these moments. Mean peak external flexion moments at the hip and ankle were 0.55 bodyweight times leg length (BWL) each whilst peak knee extension moments were about half that value (0.29 BWL). Muscles had the capacity to generate 146%, 230%, and 212 % of the mean peak external moments at the hip, knee, and ankle, respectively. Similarities in hindlimb morphology and external loading across passerine species suggest that the effective take-off strategy employed by the zebra finch may be shared across the passerine clade and therefore half of all birds.

Biomechanical Features of Drop Vertical Jump Are Different Among Various Sporting Activities

Background: Risk for non-contact anterior cruciate ligament (ACL) injury can be assessed based on drop vertical jump (DVJ). However, biomechanics of DVJ should differ with type of various sporting activities. The purpose of the present study was to clarify whether biomechanical features of DVJ are different among various sporting activities in female athletes.Methods: A total of 42 female athletes, including 25 basketball, 8 soccer and 9 volleyball players, participated in the current investigation. DVJ was done for each female athlete using a three-dimensional motion analysis system which consisted of six cameras, two force plates and 46 retro-reflective markers. Kinematic and kinetic data were recorded for both limbs in each athlete. Simultaneously, frontal and sagittal plane views of the DVJ were recorded using high-resolution two different video cameras to evaluate Landing Error Scoring System (LESS) score. Three-dimensional biomechanical parameters at the knee joint and LESS were compared among three different sporting activities.Results: Soccer players had better LESS score, compared to basketball players, while no significantly differences were found between basketball and volleyball players in LESS. In addition, peak knee flexion angle was significantly larger, and knee abduction angle at initial contact (IC), peak knee abduction angle, knee internal rotation angle, and knee abduction moment within 40 milliseconds from IC were significantly smaller in soccer players, compared to basketball players. There were no significantly differences between basketball and volleyball players in all biomechanical parameters.Conclusions: From the present study, female basketball and volleyball players have worse LESS score, greater knee abduction angle and moment, compared to female soccer players. Thus, female basketball and volleyball players are likely to have the increased risk of non-contact ACL injury during DVJ, compared to soccer players. DVJ may be useless as a screening tool of non-contact ACL injury for soccer players. Biomechanics of DVJ depends on characteristics of the athlete's primary sport.

Running Readiness Scale as an assessment of kinematics related to knee injury in female novice runners

CONTEXT Frontal and transverse plane kinematics were prospectively identified as risk factors for running-related injuries in females. The Running Readiness Scale (RRS) may allow for clinical evaluation of these kinematics. OBJECTIVES To assess reliability and validity of the RRS as an assessment of frontal and transverse plane running kinematics. DESIGN Cross-sectional SETTING University research laboratory. PATIENTS OR OTHER PARTICIPANTS 56 female novice runners. MAIN OUTCOME MEASURES 3D kinematics were collected during running and RRS tasks: hopping, plank, step-ups, single-leg squats, and wall-sit. RRS performances were assessed by 5 assessors, 3 times each. Inter- and intra-rater reliabilities of total RRS score and individual tasks were calculated using intraclass correlation coefficient and Fleiss kappa, respectively. Pearson correlation coefficients between peak joint angles measured during running and the same angles measured during RRS tasks were calculated. Peak joint angles of high vs. low scoring participants were compared. RESULTS Inter- and intra-rater reliabilities of assessment of the total RRS scores were good. Reliability of the assessment of individual tasks were moderate to almost perfect. Peak hip adduction, pelvic drop, and knee abduction during running were correlated with the same angles measured during hopping, step-ups, and single-leg squats (r=0.537–0.939). Peak knee internal rotation during running was correlated with peak knee internal rotation during step-ups (r=0.831). Runners who scored high on the RRS demonstrated less knee abduction during running. CONCLUSIONS The RRS may be an effective evaluation of knee abduction in novice runners, but evaluation criteria or tasks may need to be modified for effective assessment of pelvis and transverse plane knee kinematics.

Effect of osteopathic manipulation on gait asymmetry

Context Movement and loading asymmetry are associated with an increased risk of musculoskeletal injury, disease progression, and suboptimal recovery. Osteopathic structural screening can be utilized to determine areas of somatic dysfunction that could contribute to movement and loading asymmetry. Osteopathic manipulation treatments (OMTs) targeting identified somatic dysfunctions can correct structural asymmetries and malalignment, restoring the ability for proper compensation of stresses throughout the body. Little is currently known about the ability for OMTs to reduce gait asymmetries, thereby reducing the risk of injury, accelerated disease progression, and suboptimal recovery. Objectives To demonstrate whether osteopathic screening and treatment could alter movement and loading asymmetry during treadmill walking. Methods Forty-two healthy adults (20 males, 22 females) between the ages of 18 and 35 were recruited for this prospective intervention. Standardized osteopathic screening exams were completed by a single physician for each participant, and osteopathic manipulation was performed targeting somatic dysfunctions identified in the screening exam. Three-dimensional (3-D) biomechanical assessments, including the collection of motion capture and force plate data, were performed prior to and following osteopathic manipulation to quantify gait mechanics. Motion capture and loading data were processed utilizing Qualisys Track Manager and Visual 3D software, respectively. Asymmetry in the following temporal, kinetic, and kinematic measures was quantified utilizing a limb symmetry index (LSI): peak vertical ground reaction force, the impulse of the vertical ground reaction force, peak knee flexion angle, step length, stride length, and stance time. A 2-way repeated-measures analysis of variance model was utilized to evaluate the effects of time (pre/post manipulation) and sex (male/female) on each measure of gait asymmetry. Results Gait asymmetry in the peak vertical ground reaction force (−0.6%, p=0.025) and the impulse of the vertical ground reaction force (−0.3%, p=0.026) was reduced in males following osteopathic manipulation. There was no difference in gait asymmetry between time points in females. Osteopathic manipulation did not impact asymmetry in peak knee flexion angle, step length, stride length, or stance time. Among the participants, 59.5% (25) followed the common compensatory pattern, whereas 40.5% (17) followed the uncommon compensatory pattern. One third (33.3%, 14) of the participants showed decompensation at the occipitoatlantal (OA) junction, whereas 26.2% (11), one third (33.3%, 14), and 26.2% (11) showed decompensation at the cervicothoracic (CT), thoracolumbar (TL), and lumbosacral (LS) junctions, respectively. Somatic dysfunction at the sacrum, L5, right innominate, and left innominate occurred in 88.1% (37), 69.0% (29), 97.6% (41), and 97.6% (41) of the participants, respectively. Conclusions Correcting somatic dysfunction can influence gait asymmetry in males; the sex-specificity of the observed effects of osteopathic manipulation on gait asymmetry is worthy of further investigation. Osteopathic structural examinations and treatment of somatic dysfunctions may improve gait symmetry even in asymptomatic individuals. These findings encourage larger-scale investigations on the use of OMT to optimize gait, prevent injury and the progression of disease, and aid in recovery after surgery.

Muscle Contributions to Pre-Swing Biomechanical Tasks Influence Swing Leg Mechanics in Individuals Post-Stroke during Walking

Background Successful walking requires the execution of the pre-swing biomechanical tasks of body propulsion and leg swing initiation, which are often impaired post-stroke. While excess rectus femoris activity during swing is often associated with low knee flexion, previous work has suggested that deficits in propulsion and leg swing initiation may also contribute. The purpose of this study was to determine underlying causes of propulsion, leg swing initiation and knee flexion deficits in pre-swing and their link to stiff knee gait in stroke survivors. Methods Musculoskeletal models and forward dynamic simulations were developed for individuals post-stroke (n=15) and neurotypical participants (n=5). Linear regressions were used to evaluate the relationships between peak knee flexion, braking and propulsion symmetry, and individual muscle contributions to braking, propulsion, knee flexion in pre-swing, and leg swing initiation. Results 27% of individuals post-stroke had higher plantarflexor contributions to propulsion and 47% had higher vasti contributions to braking on their paretic leg relative to their nonparetic leg. Higher gastrocnemius contributions to propulsion were correlated to paretic propulsion symmetry (p=0.005) while soleus contributions were not. Higher vasti contributions to braking in pre-swing predicted lower knee flexion (p=0.022). The rectus femoris and iliopsoas did not directly contribute to lower knee flexion acceleration in pre-swing compared to contributions from the vasti. However, for some individuals with low knee flexion, during pre-swing the rectus femoris absorbed more power and the iliopsoas contributed less power to the paretic leg. Total muscle-tendon work done on the paretic leg in pre-swing was not correlated to knee flexion during swing. Conclusions These results emphasize the multiple causes of propulsion asymmetry in individuals post-stroke, including low plantarflexor contributions to propulsion, increased vasti contributions to braking and reliance on compensatory mechanisms. The results also show that the rectus femoris is not a major contributor to knee flexion in pre-swing, but absorbs more power from the paretic leg in pre-swing in some individuals with stiff knee gait. These results further highlight the heterogeneity of the post-stroke population and the need to identify individual causes of propulsion and knee flexion deficits to improve rehabilitation outcomes.

Isometric, Eccentric, and Concentric Strength in Trained and Untrained Older Adults: A Pilot Study

Background: Despite an overall decrease in muscular strength, older adults maintain eccentric (ECC) strength in greater proportions compared to isometric (ISO) and concentric (CON) strength. While resistance training is promoted for older adults, the impact of resistance training on ISO, ECC, and CON strength is relatively unknown. Objective: The purpose of this study was to compare peak ISO, ECC and CON knee extensor moments between trained and untrained older individuals. Methods: A quasi-experimental design with a two-group comparison, ex post facto, was conducted. Twenty older adults (8 females, 69.6 ± 6.1 years, 80.5 ± 16.4 kg, 1.7 ± 0.1 m) were allocated to two groups, one undergoing resistance training (n =10) and one not (n = 10). An isokinetic dynamometer measured ISO, ECC, and CON knee extensor moments. Peak knee extensor moments (Nm) and ECC: ISO ratio were analyzed using a Kruskal-Wallis test (α = 0.05). Spearman Rank-Order Correlations were run on paired combinations of peak ISO, ECC, and CON moments for both groups. Results: The trained group had significantly greater peak ISO moment (183.8 vs 137.1 Nm, p = 0.013, d = 1.3) but significantly lower ECC: ISO ratio (p = 0.028, d = 1.1). The trained group exhibited stronger correlations for ECC-ISO (rs = 0.79 vs. 0.65), ECC-CON (rs = 0.93 vs. 0.59), and CON-ISO (rs = 0.93 vs. 0.78) compared to the untrained group. Conclusions: The findings demonstrate older adults maintain eccentric and concentric strength, regardless of training status. However, trained participants had a more balanced ECC: ISO ratio, due to their increased peak ISO strength possibly due to their resistance training.