Phase-Specific Ground Reaction Force Analyses of Bilateral and Unilateral Jumps in Patients With ACL Reconstruction

Background: In patients who have undergone anterior cruciate ligament (ACL) reconstruction, there is a weak correlation between subjective evaluation of knee function on questionnaires and clinical or biomechanical test results. Hypothesis: Patients with lower subjective knee function will demonstrate lower ground-reaction forces (GRFs) in the operated leg and greater GRF asymmetries in both phase-specific and functional data analysis (FDA) approaches compared with patients with higher subjective knee function. Study Design: Descriptive laboratory study. Methods: The GRFs of the operated and nonoperated legs of 40 patients who previously underwent ACL reconstruction (patellar tendon) were analyzed during unilateral and bilateral countermovement jumps at a mean 2.5 years after surgery. The patients were separated into 2 groups depending on their International Knee Documentation Committee (IKDC) Subjective Form score: low IKDC and high IKDC. Results: Both phase-specific and FDA approaches showed lower GRF values in the operated compared with the nonoperated leg within the low-IKDC group during bilateral jumps. Moreover, lower GRF values were also present in the operated and nonoperated legs in the low-IKDC group compared with those of the high-IKDC group. Differences in GRFs were predominantly observed during the eccentric deceleration phase of jumping. Conclusion: Patients with previous ACL reconstruction who have limited subjective knee function have lower GRF values and greater GRF asymmetries, suggesting the use of interlimb compensation strategies. Clinical Relevance: The study results lead to a better understanding of the motor control needed during the eccentric and concentric movement phases of unilateral and bilateral jumps in patients who have undergone ACL reconstruction.