OBJECTIVES:The objectives were: 1) to determine if Achilles tendon forces change throughout a 30-minute run and 2) to characterize joint-level contributions to total support moment throughout the run in runners with Achilles tendinopathy in the return-to-sport phase of rehabilitation. DESIGN:Laboratory-based cross-sectional study with repeated measures. METHODS:Eighteen runners (6 females; mean (standard deviation) age: 44 (13) years; height: 173 (9) cm; body mass: 73 (11) kg) in the return-to-sport phase of Achilles tendinopathy rehabilitation participated. Each participant ran for 30 minutes on a force-instrumented treadmill within a three-dimensional motion capture environment. Marker trajectories and force data were sampled at 6 timepoints throughout the run. Achilles tendon force estimates as well as relative contributions of the hips, knees, and ankles to total support moment were determined at each timepoint. RESULTS:There were no significant limb-by-time interactions, or between-limb differences, but there was a significant time effect for peak Achilles tendon force, which decreased throughout the run. For relative contributions to total support moment, there were no between-limb differences. However, throughout the run, hip extension contribution decreased while knee extension contribution increased. CONCLUSIONS:Runners with Achilles tendinopathy in the return-to-sport phase of rehabilitation do not demonstrate side-to-side differences in tendon forces or contributions to total support moment. However, there are minor changes in peak tendon forces as well as hip and knee contributions to total support moment during a comfortable 30-minute run.

BACKGROUND:It is unclear why knee osteoarthritis (KOA) progresses from a unilateral to bilateral joint disease. This study aimed to evaluate relations between vertical ground reaction forces (VGRFs) while walking and structural worsening in the unaffected limb of adults with unilateral KOA. METHODS:Discrete metrics were extracted from the unaffected limb VGRF signal while walking at a self-selected speed. Structural worsening of the unaffected knee was evaluated over 2 years with radiographs (primary) and MRIs (secondary). Logistic regression models evaluated associations between VGRF metrics and structural worsening outcomes, while adjusting for relevant covariates. Similar relations were evaluated in adults without OA in either knee to determine if VGRF metrics uniquely relate to contralateral structural worsening in adults with unilateral KOA. FINDINGS:In adults with unilateral KOA (n = 262), VGRFs were not associated with radiographic joint space narrowing within the tibiofemoral compartments of the unaffected knee. Additionally, VGRFs were not associated with MRI-detected cartilage loss in the medial tibiofemoral compartment. However, for the lateral tibiofemoral compartment, higher vertical loading and unloading rates were protective against cartilage loss (Odd ratios (OR) = 0.31-0.47), while larger vertical impulses and valley magnitudes were associated with increased odds of cartilage loss (OR = 2.50 and 2.26, respectively). No relations were found in adults without OA in either knee (n = 985). INTERPRETATION:VGRF metrics lack the ability to predict medial tibiofemoral structural worsening in knees without OA. However, vertical impulse and valley magnitude can assist with identifying contralateral knees at risk for lateral tibiofemoral cartilage loss in those with unilateral KOA.

Asymmetric walking patterns are common in healthy and clinical populations. While minor asymmetries are likely benign, greater asymmetries may negatively affect physical function and mobility. Changes in mechanical work may largely explain why walking asymmetry influences physical function and mobility. Thus, the purpose of this study was to describe how increasing the degree of walking asymmetry affects limb- and joint-level mechanical work. Ten healthy participants walked on a force-instrumented split-belt treadmill for a total of 33 min. Participants began by walking for 6 min at 1.2 m/s with both treadmill belts moving at equal speeds (0 % condition). After the 0 % condition, the speed of the right belt was reduced by 10, 25, and 50 % while the left belt maintained a constant speed of 1.2 m/s. To visualize the distribution of work within each limb, pie charts were developed by calculating the relative work performed by each joint/segment to the total absolute limb work. To determine the effect of walking asymmetry on mechanical cost of transport (CoT), we constructed a 2x4 (limb-by-condition) repeated measures ANOVA model. There was a significant limb-by-condition interaction (p < 0.0001), with CoT decreasing in the fast limb and increasing in the slow limb as asymmetry increased. However, the joint-level distribution of work remained relatively unchanged across walking conditions. Therefore, inducing asymmetric walking in healthy adults appears to alter mechanical costs while only minimally affecting joint/segment-level compensations. Future research should focus on individuals with pathologies to determine if similar strategies are observed.

Objective: Determine the association of walking cadence to incident and worsening knee pain and physical function over 2 years in adults with or at risk for knee OA. Design: Participants from the Multicenter Osteoarthritis study were included. Cadence was measured using a GAITRite walkway. Incident and worsening knee symptoms, pain with walking, and functional limitations were assessed at baseline and 2 years later. The association of cadence to each outcome was analyzed using log binomial regression. Cadence was assessed continuously as a 10-unit change and categorically using quartiles. Analyses were adjusted for age, sex, race, BMI, presence of tibiofemoral OA, depression, and history of knee injury. Sensitivity analyses were conducted for all outcomes adjusted for gait speed and stratified by sex. Results: Among 1600 participants (60.3 % female, age 67.1 f 7.7 years), lower cadence was not significantly associated with incident or worsening knee symptoms, pain with walking, or functional limitations. For every 10-step/ min decrease in cadence, the risk of incident knee symptoms increased by 10 % (RR = 1.10, 95%CI [0.97, 1.25]), though this was not statistically significant and was attenuated after adjusting for gait speed (RR = 0.95, 95%CI [0.80, 1.12]). No significant associations were observed for incident or worsening pain with walking or functional limitations. Sex-stratified analyses revealed inconsistent findings, including an increased risk for incident functional limitations in females (RR = 1.45, 95%CI [1.02, 2.08]), which was attenuated after adjusting for gait speed. Conclusion: Lower cadence was not significantly associated with pain and function, suggesting that the interplay between cadence, gait speed, and clinical outcomes warrants further investigation.

To assess the feasibility of a randomized controlled trial evaluating a gait retraining program to reduce peak tibial acceleration on knee pain and impact loading in adults with knee osteoarthritis. Participants (n = 44) were randomized to a gait retraining or standard walking program. Walking duration increased from 10 to 30 minutes as feedback faded over eight sessions. Gait retraining participants received real-time biofeedback to reduce peak tibial acceleration by 20%. Feasibility criteria included rates of recruitment, enrollment, and retention and number of adverse events. Knee pain and overground impact loading were assessed at baseline and one week after the last treadmill session. Analysis of covariance models compared group differences in peak tibial acceleration, pain, and impact loading after the walking program, controlling for baseline values. Most feasibility criteria were met. From 2019 to 2023, 867 individuals were screened (~22 individuals per month), and 46 were enrolled and randomized (n = 23 per group). No adverse events were identified. Peak tibial acceleration reduced by 0.13g and 0.09g (gravitational equivalents) for the gait retraining and standard walking groups, respectively. Greater reductions in pain were observed for the standard walking group compared to the gait retraining group. Changes in impact loading were not significant in either group. No between-group differences were observed for peak tibial acceleration, knee pain, or impact loading. A full-scale randomized clinical trial is feasible with modification. However, gait retraining to reduce peak tibial acceleration was no more effective than a standard walking program for reducing knee pain and impact loading.

Gait retraining is a strategy to manage altered loading patterns and pain characteristic of knee osteoarthritis. Lower walking cadence is associated with higher knee joint loading, vertical ground reaction forces, and risk for cartilage worsening. Therefore, we determined the acute effects of increasing walking cadence on measures of lower extremity loading and knee pain in knee osteoarthritis. Twenty-five participants with knee osteoarthritis (age = 62.5 ± 7.2; 76.0 % female) walked at fixed speed on an instrumented treadmill from which baseline cadence was measured. Five, randomized experimental cadence conditions (2 %, 4 %, 6 %, 8 %, or 10 % over baseline cadence) were completed. Real-time auditory and visual feedback on cadence was provided while kinematics and ground reaction forces were sampled. Linear mixed effects models evaluated the effect of cadence on knee adduction and flexion moment peaks and impulses, impact loading metrics (vertical ground reaction force impact peak, vertical average and instantaneous loading rates), and knee pain. Increasing cadence by 2-10 % did not significantly change knee adduction moment peaks or impulse. Peak knee flexion moment increased by 3-32 % and knee flexion moment impulse reduced by 2-9 % with increases in cadence, but these results were not significant (peak knee flexion moment, p = 0.070; knee flexion moment impulse, p = 0.085). Increasing cadence significantly increased the vertical impact peak (p < 0.001), and the vertical average (p = 0.010), and instantaneous (p = 0.007) loading rates. Small increases in cadence at a fixed gait speed does not significantly change surrogate measures of knee joint loading or pain, but does increase measures of impact loading.

OBJECTIVE:The objective of this study was to identify gait alterations related to worsening knee pain and worsening physical function, using machine learning approaches applied to wearable sensor-derived data from a large observational cohort. METHODS:Participants in the Multicenter Osteoarthritis Study (MOST) completed a 20-m walk test wearing inertial sensors on their lower back and ankles. Parameters describing spatiotemporal features of gait were extracted from these data. We used an ensemble machine learning technique ("super learning") to optimally discriminate between those with and without worsening physical function and, separately, those with and without worsening pain over two years. We then used log-binomial regression to evaluate associations of the top 10 influential variables selected with super learning with each outcome. We also assessed whether the relation of altered gait with worsening function was mediated by changes in pain. RESULTS:Of 2,324 participants, 29% and 24% had worsening knee pain and function over two years, respectively. From the super learner, several gait parameters were found to be influential for worsening pain and for worsening function. After adjusting for confounders, greater gait asymmetry, longer average step length, and lower dominant frequency were associated with worsening pain, and lower cadence was associated with worsening function. Worsening pain partially mediated the association of cadence with function. CONCLUSION:We identified gait alterations associated with worsening knee pain and those associated with worsening physical function. These alterations could be assessed with wearable sensors in clinical settings. Further research should determine whether they might be therapeutic targets to prevent worsening pain and worsening function.

Purpose (the aim of the study): Knee osteoarthritis (OA) affects numerous anatomical structures (e.g., bone, cartilage, fat pad, synovium), yet limited attention has been given to the patellar and quadriceps (i.e., extensor) tendons. Changes in tendon mechanical properties are known to affect neuromechanics, musculotendinous function, and functional performance in healthy adults and those with tendon conditions (e.g., tendinopathy). Therefore, altered tendon mechanical properties could contribute to outcomes in individuals with knee OA.

Objectives: To determine the relationships between (1) Achilles tendon pain and loading symmetry, and (2) number of running bouts and symptom severity, during two weeks of outdoor running in individuals with Achilles tendinopathy. Design: Prospective, observational study. Setting: Biomechanics laboratory and outdoors. Participants: Seventeen runners with Achilles tendinopathy in the return-to-sport phase of rehabilitation. Main outcome measures: Symptom severity was recorded with the Victorian Institute of Sports AssessmentAchilles (VISA-A) questionnaire. Running bouts and Achilles tendon pain during runs were recorded with daily training logs. Ground contact time was collected during runs with wearable sensors. Linear mixed modeling determined if the relationship between Achilles tendon pain and ground contact time symmetry during running was moderated by consecutive run days. Multiple regression determined the relationship between number of running bouts and change in VISA-A scores over two weeks, adjusted for run distance. Results: Greater ground contact time on the contralateral leg corresponded to increased ipsilateral tendon pain for each consecutive run day (b = -0.028, p < 0.001). Number of running bouts was not associated with 2-week changes in VISA-A scores (p = 0.672). Conclusions: Pain during running is associated with injured leg off-loading patterns, and this relationship strengthened with greater number of consecutive run days. Number of running bouts was not related to shortterm symptom severity.

Purpose: Knee osteoarthritis (KOA) often starts as a unilateral disease and commonly progresses to bilateral KOA. There is a need to identify mechanisms that explain unilateral to bilateral KOA progression. Loading is regarded as a risk factor for KOA. Thus, we aimed to explore relations between ground reaction force (GRF) symmetry metrics and cartilage worsening in the contralateral knee in persons with unilateral KOA. Although we explored posterior and medial-lateral GRF symmetry metrics, our primary hypothesis was that higher vertical GRF peaks, loading rates, and impulses in the contralateral limb relative to OA limb would be associated with cartilage worsening in the contralateral knee over 2 years.

BACKGROUND We aimed to identify important components of, and practical resources relevant for inclusion in, a toolkit to aid exercise delivery for people with hip/knee osteoarthritis. METHOD An online international multi-disciplinary survey was conducted across 43 countries (139 clinicians, 44 people with hip/knee osteoarthritis and 135 osteoarthritis researchers). Participants were presented with the seeding statement 'Practical resources to aid the implementation of exercise for people with hip/knee osteoarthritis should…' and asked to provide up to 10 open text responses. Responses underwent refinement and qualitative content analysis to create domains and categories. RESULTS Refinement of 551 open text responses yielded 72 unique statements relevant for analysis. Statements were organised into nine broad domains, suggesting that resources to aid exercise delivery should: (1) be easily accessible; (2) be of high quality; (3) be developed by, and for, stakeholders; (4) include different ways of delivering information; (5) include different types of resources to support exercise and non-exercise components of self-management; (6) include resources on recommended exercises and how to perform/progress them; (7) include tools to support motivation and track progress; (8) include resources to enable tailoring of the programme to the individual and; (9) facilitate access to professional and peer support. CONCLUSION Our findings identified important components of, and practical resources to include within, a toolkit to aid delivery of exercise for people with hip/knee osteoarthritis. These findings have implications for exercise providers and lay the foundation for the development of a toolkit to help ensure exercise provision aligns with current international recommendations.