Acute Effect of Altered Mechanical Loading on Biomechanics and Biochemical Markers in Individuals with Anterior Cruciate Ligament Reconstruction

Context: The complex interaction between aberrant mechanical loading and altered cartilage metabolism is hypothesized to lead to the development of posttraumatic osteoarthritis (PTOA) following anterior cruciate ligament reconstruction (ACLR). There is a critical need for effective therapeutic strategies that are capable of manipulating mechanical loading for the purpose of maintaining homeostatic cartilage metabolism following ACLR. Objective: To utilize real-time biofeedback to acutely increase (i.e. overloading), acutely decrease (i.e. under-loading) and promote symmetrical loading between limbs during walking gait in individuals with ACLR to determine changes in lower extremity biomechanical outcomes and cartilage metabolism that occur following acute bouts of altered mechanical loading. Participants: 30 individuals with a primary, unilateral ACLR. Interventions: Participants completed four testing sessions. One of four loading conditions was completed during 20 minutes of treadmill walking, and included 1) control condition of normal walking, 2) a 5% increase (i.e. overloading) in peak vGRF, 3) a 5% decrease (i.e. under-loading) in peak vGRF, and 4) symmetrical peak vGRF between limbs. Main Outcome Measures: Root mean square error (RMSE) was calculated during the acquisition and recall periods. Lower biomechanical outcomes included peak vGRF, instantaneous vGRF loading rate, peak KEM, and knee flexion excursion. Catilage metabolism was quantified using serum oligomeric matrix protein (COMP). Results: Individuals with ACLR demonstrate lesser RMSE during the acquisition of symmetrical loading as compared to the overloading and under-loading conditions. Peak vGRF was significantly greater during the overloading condition, and significantly lesser during the under-loading condition as compared to the control condition. Peak KEM and knee flexion excursion were significantly greater during the overloading condition as compared to the under-loading condition. Individuals with ACLR demonstrating an increase in COMP during the control condition demonstrated a significant decrease in COMP during the overloading condition as compared to the control. Individuals with ACLR demonstrating a lesser baseline peak vGRF also demonstrated a greater increase in COMP following 20 minutes of normal walking. Conclusions: Real-time biofeedback may be beneficial for altering mechanical loading during walking gait in individuals with ACLR. Acutely manipulating mechanical during walking gait may be able to influence cartilage metabolism in individuals with ACLR.Doctor of Philosoph