Muscle forces and fascicle behavior during three hamstring exercises.

Knowledge about muscular forces and fascicle behavior during hamstring exercises can optimize exercise prescription, but information on these outcomes across different exercises is lacking. We aimed to characterize and compare lower-limb muscle forces and biceps femoris long head muscle fascicle behavior between three hamstring exercises: the Nordic hamstring curl (NHC), single-leg Roman chair (RCH), and single-leg deadlift (DL). Ten male participants performed the exercises while full-body kinematics, ground reaction forces, surface muscle activation, and biceps femoris long head fascicle behavior were measured. Mean fascicle length was highest in the DL, followed by the RCH and NHC. Fascicle lengthening was higher in the NHC compared with the RCH and DL, with no difference between the RCH and DL. Biceps femoris short and long head, semitendinosus, and semimembranosus peak forces were generally higher in the NHC compared with the RCH and DL, while mean forces during the eccentric phase were generally not different between the NHC and RCH. Peak forces in the NHC coincided with low biceps femoris long head and semimembranosus muscle activation. The NHC generally has the highest peak hamstring muscle forces and results in more fascicle lengthening when compared to the DL and RCH. The NHC may therefore be most effective to promote increases in fascicle length. While the NHC may be effective to promote biceps femoris short head and semitendinosus strength adaptations, the RCH and DL may be more effective to promote strength increases in the biceps femoris long head and semimembranosus.

Single leg vertical jump performance identifies knee function deficits at return to sport after ACL reconstruction in male athletes.

OBJECTIVES: Vertical jump performance (height) is a more representative metric for knee function than horizontal hop performance (distance) in healthy individuals. It is not known what the biomechanical status of athletes after anterior cruciate ligament (ACL) reconstruction (ACLR) is at the time they are cleared to return to sport (RTS) or whether vertical performance metrics better evaluate knee function. METHODS: Standard marker-based motion capture and electromyography (EMG) were collected from 26 male athletes cleared to RTS after ACLR and 22 control healthy subjects during single leg vertical jumps (SLJ) and single leg drop jumps (SLDJ). Performance outcomes, jump height and the Reactive Strength Index, were calculated. Sagittal plane kinematics, joint moments and joint work were obtained using inverse dynamics and lower limb muscle forces were computed using an EMG-constrained musculoskeletal model. Muscle contribution was calculated as a percentage of the impulse of all muscle forces in the model. Between-limb and between-group differences were explored using mixed models analyses. RESULTS: Jump performance, assessed by jump height and Reactive Strength Index, was significantly lower in the involved than the uninvolved limb and controls, with large effect sizes. For the ACLR group, jump height limb symmetry index was 83% and 77% during the SLJ and SLDJ, respectively. Work generation was significantly less in the involved knee compared to uninvolved limb and controls during the SLJ (p<0.001; d=1.19; p=0.003, d=0.91, respectively) and during the SLDJ (p<0.001; d=1.54; p=0.002, d=1.05, respectively). Hamstrings muscle contribution was greater in the involved compared to the uninvolved limb and controls, whereas soleus contribution was lower in the involved limb compared to controls. CONCLUSIONS: During vertical jumps, male athletes after ACLR at RTS still exhibit knee biomechanical deficits, despite symmetry in horizontal functional performance and strength tests. Vertical performance metrics like jump height and RSI can better identify interlimb asymmetries than the more commonly used hop distance and should be included in the testing battery for the RTS.

Single leg hop for distance symmetry masks lower limb biomechanics: time to discuss hop distance as decision criterion for return to sport after ACL reconstruction?

BACKGROUND: We evaluated the lower limb status of athletes after anterior cruciate ligament reconstruction (ACLR) during the propulsion and landing phases of a single leg hop for distance (SLHD) task after they had been cleared to return to sport. We wanted to evaluate the biomechanical components of the involved (operated) and uninvolved legs of athletes with ACLR and compare these legs with those of uninjured athletes (controls). METHODS: We captured standard video-based three-dimensional motion and electromyography (EMG) in 26 athletes after ACLR and 23 healthy controls during SLHD and calculated lower limb and trunk kinematics. We calculated lower limb joint moments and work using inverse dynamics and computed lower limb muscle forces using an EMG-constrained musculoskeletal modelling approach. Between-limb (within ACLR athletes) and between-group differences (between ACLR athletes and controls) were evaluated using paired and independent sample t-tests, respectively. RESULTS: Significant differences in kinematics (effect sizes ranging from 0.42 to 1.56), moments (0.39 to 1.08), and joint work contribution (0.55 to 1.04) were seen between the involved and uninvolved legs, as well as between groups. Athletes after ACLR achieved a 97%±4% limb symmetry index in hop distance but the symmetry in work done by the knee during propulsion was only 69%. During landing, the involved knee absorbed less work than the uninvolved, while the uninvolved knee absorbed more work than the control group. Athletes after ACLR compensated for lower knee work with greater hip work contribution and by landing with more hip flexion, anterior pelvis tilt, and trunk flexion. CONCLUSION: Symmetry in performance on a SLHD test does not ensure symmetry in lower limb biomechanics. The distance hopped is a poor measure of knee function, and largely reflects hip and ankle function. Male athletes after ACLR selectively unload the involved limb but outperform controls on the uninvolved knee.

Impact of Gender and Feature Set on Machine-Learning-Based Prediction of Lower-Limb Overuse Injuries Using a Single Trunk-Mounted Accelerometer.

Even though practicing sports has great health benefits, it also entails a risk of developing overuse injuries, which can elicit a negative impact on physical, mental, and financial health. Being able to predict the risk of an overuse injury arising is of widespread interest because this may play a vital role in preventing its occurrence. In this paper, we present a machine learning model trained to predict the occurrence of a lower-limb overuse injury (LLOI). This model was trained and evaluated using data from a three-dimensional accelerometer on the lower back, collected during a Cooper test performed by 161 first-year undergraduate students of a movement science program. In this study, gender-specific models performed better than mixed-gender models. The estimated area under the receiving operating characteristic curve of the best-performing male- and female-specific models, trained according to the presented approach, was, respectively, 0.615 and 0.645. In addition, the best-performing models were achieved by combining statistical and sports-specific features. Overall, the results demonstrated that a machine learning injury prediction model is a promising, yet challenging approach.

Movement Quality Parameters during Gait Assessed by a Single Accelerometer in Subjects with Osteoarthritis and Following Total Joint Arthroplasty.

This study's aim is threefold: (I) Evaluate movement quality parameters of gait in people with hip or knee osteoarthritis (OA) compared to asymptomatic controls from a single trunk-worn 3D accelerometer. (II) Evaluate the sensitivity of these parameters to capture changes at 6-weeks, 3-, 6-, and 12-months following total knee arthroplasty (TKA). (III) Investigate whether observed changes in movement quality from 6-weeks and 12-months post-TKA relates to changes in patient-reported outcome measures (PROMs). We invited 20 asymptomatic controls, 20 people with hip OA, 18 people pre- and post-TKA to our movement lap. They wore a single trunk-worn accelerometer and walked at a self-selected speed. Movement quality parameters (symmetry, complexity, smoothness, and dynamic stability) were calculated from the 3D acceleration signal. Between groups and between timepoints comparisons were made, and changes in movement quality were correlated with PROMs. We found significant differences in symmetry and stability in both OA groups. Post-TKA, most parameters reflected an initial decrease in movement quality at 6-weeks post-TKA, which mostly normalised 6-months post-TKA. Finally, improved movement quality relates to improvements in PROMs. Thus, a single accelerometer can characterise movement quality in both OA groups and post-TKA. The correlation shows the potential to monitor movement quality in a clinical setting to inform objective, data-driven personalised rehabilitation.

Measuring only hop distance during single leg hop testing is insufficient to detect deficits in knee function after ACL reconstruction: a systematic review and meta-analysis.

OBJECTIVE: To systematically review the biomechanical deficits after ACL reconstruction (ACLR) during single leg hop for distance (SLHD) testing and report these differences compared with the contralateral leg and with healthy controls. DESIGN: Systematic review with meta-analysis. DATA SOURCES: A systematic search in Pubmed (Ovid), EMBASE, CINAHL, Scopus, Web of Science, PEDro, SPORTDiscus, Cochrane Library, grey literature and trial registries, was conducted from inception to 1 April 2018. ELIGIBILITY CRITERIA FOR SELECTING STUDIES: Studies reporting kinematic, kinetic and/or electromyographic data of the ACLR limb during SLHD with no language limits. RESULTS: The literature review yielded 1551 articles and 19 studies met the inclusion criteria. Meta-analysis revealed strong evidence of lower peak knee flexion angle and knee flexion moments during landing compared with the uninjured leg and with controls. Also, moderate evidence (with large effect size) of lower knee power absorption during landing compared with the uninjured leg. No difference was found in peak vertical ground reaction force during landing. Subgroup analyses revealed that some kinematic variables do not restore with time and may even worsen. CONCLUSION: During SLHD several kinematic and kinetic deficits were detected between limbs after ACLR, despite adequate SLHD performance. Measuring only hop distance, even using the healthy leg as a reference, is insufficient to fully assess knee function after ACLR. PROSPERO trial registration number CRD42018087779.

OpenSim Versus Human Body Model: A Comparison Study for the Lower Limbs During Gait.

Musculoskeletal modeling and simulations have become popular tools for analyzing human movements. However, end users are often not aware of underlying modeling and computational assumptions. This study investigates how these assumptions affect biomechanical gait analysis outcomes performed with Human Body Model and the OpenSim gait2392 model. The authors compared joint kinematics, kinetics, and muscle forces resulting from processing data from 7 healthy adults with both models. Although outcome variables had similar patterns, there were statistically significant differences in joint kinematics (maximal difference: 9.8° [1.5°] in sagittal plane hip rotation), kinetics (maximal difference: 0.36 [0.10] N·m/kg in sagittal plane hip moment), and muscle forces (maximal difference: 8.51 [1.80] N/kg for psoas). These differences might be explained by differences in hip and knee joint center locations up to 2.4 (0.5) and 1.9 (0.2) cm in the posteroanterior and inferosuperior directions, respectively, and by the offset in pelvic reference frames of about 10° around the mediolateral axis. The choice of model may not influence the conclusions in clinical settings, where the focus is on interpreting deviations from the reference data, but it will affect the conclusions of mechanical analyses in which the goal is to obtain accurate estimates of kinematics and loading.

In-silico techniques to inform and improve the personalized prescription of shoe insoles.

Background: Corrective shoe insoles are prescribed for a range of foot deformities and are typically designed based on a subjective assessment limiting personalization and potentially leading to sub optimal treatment outcomes. The incorporation of in silico techniques in the design and customization of insoles may improve personalized correction and hence insole efficiency. Methods: We developed an in silico workflow for insole design and customization using a combination of measured motion capture, inverse musculoskeletal modelling as well as forward simulation approaches to predict the kinematic response to specific insole designs. The developed workflow was tested on twenty-seven participants containing a combination of healthy participants (7) and patients with flatfoot deformity (20). Results: Average error between measured and simulated kinematics were 4.7 ± 3.1, 4.5 ± 3.1, 2.3 ± 2.3, and 2.3 ± 2.7° for the chopart obliquity, chopart anterior-posterior axis, tarsometatarsal first ray, and tarsometatarsal fifth ray joints respectively. Discussion: The developed workflow offers distinct advantages to previous modeling workflows such as speed of use, use of more accessible data, use of only open-source software, and is highly automated. It provides a solid basis for future work on improving predictive accuracy by adapting the currently implemented insole model and incorporating additional data such as plantar pressure.

Musculoskeletal-Modeling-Based, Full-Body Load-Assessment Tool for Ergonomists (MATE): Method Development and Proof of Concept Case Studies.

A new ergonomic-risk-assessment tool was developed that combines musculoskeletal-model-based loading estimates with insights from fatigue failure theory to evaluate full-body musculoskeletal loading during dynamic tasks. Musculoskeletal-modeling output parameters, i.e., joint contact forces and muscle forces, were combined with tissue-specific injury thresholds that account for loading frequency to determine the injury risk for muscles, lower back, and hip cartilage. The potential of this new risk-assessment tool is demonstrated for defining ergonomic interventions in terms of lifting characteristics, back and shoulder exoskeleton assistance, box transferring, stoop lifting, and an overhead wiring task, respectively. The MATE identifies the risk of WMSDs in different anatomical regions during occupational tasks and allows for the evaluation of the impact of interventions that modify specific lifting characteristics, i.e., load weight versus task repetition. Furthermore, and in clear contrast to currently available ergonomic assessment scores, the effects of the exoskeleton assistance level on the risk of WMSDs of full-body musculoskeletal loading (in particular, the muscles, lower back, and hips) can be evaluated and shows small reductions in musculoskeletal loading but not in injury risk. Therefore, the MATE is a risk-assessment tool based on a full-body, musculoskeletal-modeling approach combined with insights from the fatigue failure theory that shows the proof of concept of a shoulder and back exoskeleton. Furthermore, it accounts for subject-specific characteristics (age and BMI), further enhancing individualized ergonomic-risk assessment.

External weight mass and carrying position influence peak patellar tendon force and patellofemoral joint contact force independently during forward lunge.

BACKGROUND: The forward lunge is a common exercise in the rehabilitation of patellar tendinopathy and patellofemoral pain syndrome. External weights are frequently used to increase the peak patellar tendon force and patellofemoral joint contact force during this exercise. The weight's position might influence this relationship. The objective of this study was to investigate the combined effect of an external weight's mass and carrying position on the peak patellar tendon force and patellofemoral joint contact force during a forward lunge. METHODS: Ten healthy individuals performed forward lunges holding external weights between 0.1 and 0.3 times body mass either in one hand at the ipsilateral or contralateral side of the leading leg, or in two hands at the side or in front of the trunk. Three-dimensional kinematic data and ground reaction forces were collected and peak patellar tendon force and patellofemoral joint contact force were calculated using musculoskeletal modelling. Two-way repeated measures ANOVA's determined the main effects for the external weight's mass and position as well as their interaction effect. FINDINGS: Increasing the mass of the external weights increased both the peak patellar tendon force and patellofemoral joint contact force linearly and at the same rate in all positions. Both peak forces were larger in the one-hand ipsilateral and two-hand side positions. INTERPRETATION: An external weight's mass and position both influence the peak patellar tendon force and patellofemoral joint contact force during a forward lunge. The rate of increase in peak forces with increasing mass was similar for all weight-carrying positions.

Comparison of the Effect of Dressage Rider Skill Level on Physical Fitness Parameters and Posture on an Equestrian Simulator.

In dressage riding, rider posture plays an important role in the performance of the exercises. The purpose of this study was to compare physical fitness and posture on an equestrian simulator between different competitive dressage rider skill levels. Participants (ten expert and twelve novice competitive dressage riders) performed a physiotherapeutic screening test and an equestrian simulator test. The expert rider group (G2) had less variability in both left (P = .002) and right (P = .021) rein force during medium canter on the simulator compared to the novice rider group (G1). The shoulder angle of the expert riders was larger in all gaits. These findings indicate that the ability to maintain a constant force on the reins and a dynamically stable hand position during riding on a simulator are important indicators for good rider performance. Expert riders presented a trend toward a more stable posture on the simulator as indicated by the reduced trunk variability (P = .034 vs. CV = 0.011) and smaller trunk ROM (P = .012 vs. CV = 0.011) and knee ROM (P = .033 vs. CV = 0.011) in the collected canter and collected walk respectively. These kinematic differences underscore their capability of maintaining a continued and constant force on the reins, but these findings require further research. No significant differences were found between groups in the physiotherapeutic screening. This underlines the difficulty in identifying the physical factors contributing to better rider performance. In conclusion, the current study shows that "stable rein contact" is the main difference between novice and expert competitive dressage riders on the simulator.

Using musculoskeletal modelling to estimate knee joint loading pre and post high tibial osteotomy.

BACKGROUND: Both medial knee osteoarthritis and associated varus alignment have been proposed to alter knee joint loading and consequently overloading the medial compartment. Individuals with knee osteoarthritis and varus deformity are candidates for coronal plane corrective surgery, high tibial osteotomy. This study evaluated knee loading and contact location for a control group, a pre-surgery cohort and the same cohort 12 months post-surgery using a musculoskeletal modelling approach. METHODS: Joint kinematics during gait were measured in 30 knee osteoarthritis patients, before and after high tibial osteotomy, and 28 healthy adults. Using a musculoskeletal model that incorporated patient-specific mechanical tibial femoral angle, the resulting muscle, ligament, and contact forces were calculated and the medial - lateral condyle load distribution was analysed. FINDINGS: Surgery changed medial compartment contact force throughout stance relative to pre-surgery. This reduction in medial compartment contact force pre- vs post-HTO is observed despite a significant increase in post-surgery walking speed compared to pre-HTO, where increased speed is typically associated with increased joint loading. INTERPRETATION: This study has estimated the effects of high tibial osteotomy on knee loading using a generic model that incorporates a detailed knee model to better understand tibiofemoral contact loading. The findings support the aim of surgery to unload the medial knee compartment and lateralise joint contact forces.

The biomechanical fingerprint of hip and knee osteoarthritis patients during activities of daily living.

BACKGROUND: Osteoarthritis is a highly prevalent disease affecting the hip and knee joint and is characterized by load-mediated pain and decreased quality of life. Dependent on involved joint, patients present antalgic movement compensations, aiming to decrease loading on the involved joint. However, the associated alterations in mechanical loading of the ipsi- and contra-lateral lower limb joints, are less documented. Here, we documented the biomechanical fingerprint of end-stage hip and knee osteoarthritis patients in terms of ipsilateral and contralateral hip and knee loading during walking and stair ambulation. METHODS: Three-dimensional motion-analysis was performed in 20 hip, 18 knee osteoarthritis patients and 12 controls during level walking and stair ambulation. Joint contact forces were calculated using a standard musculoskeletal modelling workflow in Opensim. Involved and contralateral hip and knee joint loading was compared against healthy controls using independent t-tests (p < 0.05). FINDINGS: Both hip and knee cohorts significantly decreased loading of the involved joint during gait and stair ambulation. Hip osteoarthritis patients presented no signs of ipsilateral knee nor contralateral leg overloading, during walking and stair ascending. However, knee osteoarthritis patients significantly increased loading at the ipsilateral hip, and contralateral hip and knee joints during stair ambulation compared to controls. INTERPRETATION: The biomechanical fingerprint in knee and hip osteoarthritis patients confirmed antalgic movement strategies to unload the involved leg during gait. Only during stair ambulation in knee osteoarthritis patients, movement adaptations were confirmed that induced unbalanced intra- and inter-limb loading conditions, which are known risk factors for secondary osteoarthritis.

Anterior Tibiotalar Fat Pad Involvement in Ankle Osteoarthritis: MRI Features in Patients 1 Year After a Lateral Ankle Sprain.

OBJECTIVE: To investigate the characteristics of the anterior tibiotalar fat pad (ATFP) in the ankle joint in a population of patients 1 year after an ankle sprain and its correlation with systemic factors and local articular pathology. DESIGN: The study is a secondary analysis of an observational case-control study. We included 206 patients who were followed 6-12 months after ankle sprain. T1 MRI scans were assessed for signal intensity and area of ATFP by mapping the fat pad using dedicated imaging software (Mimics 18.0). Quantitative values of intensity and area were generated. Linear regression analysis was used to examine the association between both local and systemic factors and the ATFP. Variables with a P value <0.2 were entered in 5 stepwise multivariate models: (1) age-sex-body mass index (BMI); (2) anamnesis; (3) physical examination; (4) radiographic findings; and (5) MRI findings. Predictors in these separate models were entered in the final model. RESULTS: The final multivariate model showed a significant positive association between age (P = 0.04; 95% confidence interval [CI] = 1.13 ± 1.06), BMI (P = 0.05; 95% CI = 3.61 ± 3.53), and sex (P < 0.01; 95% CI = -49.26 ± 30.04) with T1 intensity. The final model also showed a significant negative association between age (P < 0.01; 95% CI = -0.57 ± 0.34), diffuse cartilage loss in the lateral talus (P = 0.03; 95% CI = -0.71 ± 0.63), and Kellgren and Lawrence score in the tibiotalar joint (P < 0.01; 95%CI = -21.61 ± 7.24) and ATFP area. A positive association was found between BMI (P < 0.01; 95% CI = 2.25 ± 1.15) and ATFP area. CONCLUSION: This study demonstrates a correlation between ATFP and both systemic factors and local pathology in the ankle joint.

The Exo4Work shoulder exoskeleton effectively reduces muscle and joint loading during simulated occupational tasks above shoulder height.

INTRODUCTION: Excessive physical shoulder musculoskeletal loading (muscle and joint contact forces), known to contribute to work-related shoulder disorders, can be reduced by a passive shoulder exoskeleton during quasi-static tasks. However, its effect on neighboring joints i.e. elbow, lower back, hip, and knee and its effect on joint contact forces have not been investigated. Furthermore, the effect of the exoskeleton's assistance versus movement adaptation when wearing the exoskeleton on musculoskeletal loading remains unexplored. METHODS: 3D motion capture and ground reaction forces were measured while 16 participants performed 5 simulated occupational tasks with and without the exoskeleton. A musculoskeletal modeling workflow was used to calculate musculoskeletal loading. Shoulder muscle fatigue was quantified using surface EMG. In addition, exoskeletons usability was quantified using the system usability scale. RESULTS: When wearing the passive shoulder exoskeleton, shoulder and elbow musculoskeletal loading decreased during the high lift and overhead wiring task, without increasing the musculoskeletal load at the back, hip and knee. In contrast, musculoskeletal loading in the shoulder, as well as in the knee increased while lifting a box from the ground to knee height and from elbow height to shoulder height. When wearing the exoskeleton, muscle activity of the Trapezius descendens, Deltoideus medius and Biceps brachii were reduced during the high lift. CONCLUSION: The passive shoulder exoskeleton reduces musculoskeletal loading in the lower back, shoulder and elbow during simulated occupational tasks above shoulder height. In contrast, for tasks below shoulder height, the use of the exoskeleton needs to be critically reviewed to avoid increased musculoskeletal loading also in neighboring joints due to altered movement execution when wearing the exoskeleton.

Machine-learned-based prediction of lower extremity overuse injuries using pressure plates.

Although running has many benefits for both the physical and mental health, it also involves the risk of injuries which results in negative physical, psychological and economical consequences. Those injuries are often linked to specific running biomechanical parameters such as the pressure pattern of the foot while running, and they could potentially be indicative for future injuries. Previous studies focus solely on some specific type of running injury and are often only applicable to a gender or running-experience specific population. The purpose of this study is, for both male and female, first-year students, (i) to predict the development of a lower extremity overuse injury in the next 6 months based on foot pressure measurements from a pressure plate and (ii) to identify the predictive loading features. For the first objective, we developed a machine learning pipeline that analyzes foot pressure measurements and predicts whether a lower extremity overuse injury is likely to occur with an AUC of 0.639 and a Brier score of 0.201. For the second objective, we found that the higher pressures exerted on the forefoot are the most predictive for lower extremity overuse injuries and that foot areas from both the lateral and the medial side are needed. Furthermore, there are two kinds of predictive features: the angle of the FFT coefficients and the coefficients of the autoregressive AR process. However, these features are not interpretable in terms of the running biomechanics, limiting its practical use for injury prevention.

Maximal lateral ligament strain and loading during functional activities: Model-based insights for ankle sprain prevention and rehabilitation.

BACKGROUND: Although it is generally accepted that sports activities present a high risk of lateral ligament injury, the extent to which ligaments are loaded during functional activities is less explored. This is relevant when considering ankle sprain prevention and staged rehabilitation following ligament sprain or reinforcing surgery. Therefore, anterior talofibular ligament, calcaneofibular ligament and posterior talofibular ligament strain and loading were evaluated, based on a newly developed loading index, during movements executed during daily life and rehabilitation. METHODS: Three-dimensional motion analysis data was acquired in 10 healthy volunteers during eleven different movements and processed using musculoskeletal modelling. Maximal lateral ligament strain and ligament loading, based on an new index accounting for the ankle and subtalar moment magnitude, ligament strain magnitude and duration, were calculated and statistically compared to ligament strain and loading during walking and a reference clinical (talar tilt) test. FINDINGS: Anterior talofibular, calcaneofibular and posterior talofibular lateral ligament loading were highest during vertical drop jumps, medio-lateral single leg hops and running. Additionally, anterior talofibular loading was high during stair descending, calcaneofibular loading during single leg stance without visual feedback and posterior talofibular loading during anterior single leg hops. During the clinical test, anterior talofibular and calcaneofibular ligament strain were substantially lower than the maximal strain during different movements. INTERPRETATION: Our results allow classification of exercises according to the ligament loading index and maximal strain, thereby providing objective data to progressively stage ligament loading during rehabilitation.

Symmetry in Triple Hop Distance Hides Asymmetries in Knee Function After ACL Reconstruction in Athletes at Return to Sports.

BACKGROUND: After anterior cruciate ligament reconstruction (ACLR), a battery of strength and hop tests is frequently used to determine the readiness of an athlete to successfully return to sports. However, the anterior cruciate ligament reinjury rate remains alarmingly high. PURPOSE: To evaluate the lower limb function of athletes after ACLR at the time when they had been cleared to return to sports (RTS). We aimed to evaluate if passing discharge criteria ensures restoration of normal lower limb biomechanics in terms of kinematics, kinetics, work, and percentage work contribution during a triple hop for distance. STUDY DESIGN: Controlled laboratory study. METHODS: Integrated 3-dimensional motion analysis was performed in 24 male athletes after ACLR when cleared to RTS and 23 healthy male controls during the triple-hop test. The criteria for RTS were (1) clearance by the surgeon and the physical therapist, (2) completion of a sports-specific on-field rehabilitation program, and (3) limb symmetry index >90% after quadriceps strength and hop battery tests. Lower limb and trunk kinematics, as well as knee joint moments and work, were calculated. Between-limb differences (within athletes after ACLR) and between-group differences (between ACLR and control groups) were evaluated using mixed linear models. RESULTS: Although achieving 97% limb symmetry in distance hopped and displaying almost 80% symmetry for knee work absorption in the second rebound and third landing, the ACLR cohorts demonstrated only 51% and 66% limb symmetry for knee work generation in the first and second rebound phases, respectively. During both work generation phases of the triple hop, the relative contribution of the involved knee was significantly smaller, with a prominent compensation from the hip joint (P < .001, for all phases) as compared with the uninvolved limb and the controls. In addition, patients deployed a whole body compensatory strategy to account for the between-limb differences in knee function, mainly at the hip, pelvis, and trunk. CONCLUSION: Symmetry in the triple hop for distance masked important deficits in the knee joint work. These differences were more prominent during work generation (concentric-propulsive) than work absorption (eccentric-landing). CLINICAL RELEVANCE: Symmetry in hop distance during the triple hop test masked significant asymmetries in knee function after ACLR and might not be the appropriate outcome to use as a discharge criterion. Differences between limbs in athletes after ACLR were more prominent during the power generation than the absorption phase.

Between-Limb Symmetry in ACL and Tibiofemoral Contact Forces in Athletes After ACL Reconstruction and Clearance for Return to Sport.

Background: Current return-to-sport (RTS) criteria after anterior cruciate ligament (ACL) reconstruction (ACLR) include demonstrating symmetry in functional and strength tests. It remains unknown if at the time that athletes are cleared to RTS, they exhibit between-limb symmetry in ACL and tibiofemoral contact forces or if these forces are comparable with those in uninjured athletes. Purposes: To (1) examine ACL and tibiofemoral contact forces in athletes who underwent ACLR and were cleared to RTS and (2) compare the involved leg to the healthy contralateral leg and healthy controls during functional tasks. Study Design: Cross-sectional study; Level of evidence, 3. Methods: A total of 26 male athletes who underwent ACLR were tested at the time of RTS during tasks that included single-leg vertical, horizontal, and side jumps; cutting maneuvers; and high-intensity running. We used an electromyography-constrained musculoskeletal modeling workflow to estimate ACL and tibiofemoral contact forces and compared the results with those of 23 healthy male participants. Results: The ACLR group presented no differences in peak tibiofemoral contact forces in the involved limb compared with the control group. However, there were significant between-limb differences mainly due to higher contact forces in the uninvolved (healthy) limb of the ACLR group compared with the control group. In the ACLR group, ACL forces were significantly higher in the uninvolved limb compared with the involved limb during cutting and running. Lateral contact forces were lower in the involved compared with the uninvolved limb, with large effect sizes during cutting (d = 1.14; P < .001) and running (d = 1.10; P < .001). Conclusion: Current discharge criteria for clearance to RTS after ACLR did not ensure the restoration of symmetric loading in our cohort of male athletes. ACL force asymmetry was observed during cutting and running, in addition to knee loading asymmetries on several tasks tested.

Joint kinematics alone can distinguish hip or knee osteoarthritis patients from asymptomatic controls with high accuracy.

Osteoarthritis (OA) is one of the leading musculoskeletal disabilities worldwide, and several interventions intend to change the gait pattern in OA patients to more healthy patterns. However, an accessible way to follow up the biomechanical changes in a clinical setting is still missing. Therefore, this study aims to evaluate whether we can use biomechanical data collected from a specific activity of daily living to help distinguish hip OA patients from controls and knee OA patients from controls using features that potentially could be measured in a clinical setting. To achieve this goal, we considered three different classes of statistical models with different levels of data complexity. Class 1 is kinematics based only (clinically applicable), class 2 includes joint kinetics (semi-applicable under the condition of access to a force plate or prediction models), and class 3 uses data from advanced musculoskeletal modeling (not clinically applicable). We used a machine learning pipeline to determine which classification model was best. We found 100% classification accuracy for KneeOA-vs-Asymptomatic and 93.9% for HipOA-vs-Asymptomatic using seven features derived from the lumbar spine and hip kinematics collected during ascending stairs. These results indicate that kinematical data alone can distinguish hip or knee OA patients from asymptomatic controls. However, to enable clinical use, we need to validate if the classifier also works with sensor-based kinematical data and whether the probabilistic outcome of the logistic regression model can be used in the follow-up of patients with OA.