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.