Total Support Moment Analysis Of The Stop-jump Task In Individuals Following Anterior Cruciate Ligament Reconstruction

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Purpose: To examine total support moment in the sagittal plane and individual contribution from each joint during a dynamic sport task to understand the presence of compensatory strategies in a cohort of individuals who have undergone anterior cruciate ligament reconstruction (ACLR) and have been cleared for return-to-sport (RTS) Methods: Twenty-six individuals with unilateral ACLR and RTS clearance participated in the study (20.9 ± 6.6 years; 10.0 ± 1.7 months since surgery). Each participant completed a single-leg and double-leg stop jump task. These tasks were assessed using force plates and a 3D motion analysis system. Bilateral internal hip flexor/extensor, knee flexor/extensor, and ankle plantarflexor/dorsiflexor moments were calculated at peak vertical ground reaction force. The total support moment was calculated by summing these moments for each leg and the individual percent contribution was calculated. Paired t-tests were used to assess between-limb differences for each stop jump task in the following variables of interest: total support moment; hip, knee and ankle joint contributions to the total support moment; hip, knee and ankle moments; and peak vertical ground reaction force. Wilcoxon Signed Rank tests were used to compare variables that were not normally distributed. Statistical significance was set a priori at <0.05. Results: Internal knee extensor moment was lower in the involved limb compared to the uninvolved for both tasks (17.6%, P = 0.022; 18.4%, P = 0.008). The involved limb exhibited 18.2% decrease in knee joint contribution (P = 0.01) and 21.6% increase in ankle joint contribution (P = 0.016) to the total support moment compared to the uninvolved limb in the single-leg stop jump task. No significant between-limb differences were found for the total support moment. Conclusion: Following clearance for RTS, altered knee loading is still observed. These results suggest that compensation for the involved knee is likely due to redistribution of load to the knee of the uninvolved limb or to adjacent joints of the involved limb. A partial shift in joint contribution from the knee to the ankle during the single-leg stop jump task demonstrates intralimb compensation. Further studies are needed to investigate how these adaptations impact the prevalence of subsequent injury and poor joint health.