Quadriceps Function is Associated with Running Kinetics Post Anterior Cruciate Ligament Reconstruction

Abstract

PURPOSE: Individuals with anterior cruciate ligament reconstruction (ACLR) are at greater risk for knee osteoarthritis (KOA), partially due to chronic quadriceps dysfunction. Impaired quadriceps function contributes to higher loading rates during gait, and may exacerbate cartilage breakdown. The purpose of this study was to examine the association between indices of quadriceps function and ground reaction forces (GRF) characteristics linked to KOA development during running in individuals with ACLR. METHODS: Quadriceps function and running biomechanics were assessed in 20 individuals (5 M, 15 F) with unilateral ACLR (age=22.3±3.3 years, height=1.73±0.09m; mass=71.8±15.3kg). Indices of quadriceps function included isometric peak torque (PT) and rate of torque development (RTD), and isokinetic peak torque measured at 180°/s and 240°/s. Kinetic data included peak vertical impact force (PIF), average vertical loading rate (ALR), and instantaneous vertical loading rate (ILR) acquired from the ACLR limb while running at a self-selected pace. Partial correlations were used to assess the relationship between quadriceps function and running kinetics after accounting for self-selected running speed. RESULTS: Quadriceps RTD was negatively correlated with PIF (r=-0.40, p=0.04) and ALR (r=-0.48, p=0.03). A trend was observed between quadriceps RTD and ILR (r=-0.36, p=0.07). Neither isometric PT nor isokinetic PT at 180°/second or 240°/second were associated with any running biomechanics variable. CONCLUSIONS: Slower quadriceps RTD were associated with larger PIF and ALR during running. The ability of the quadriceps to generate rapid force prior to heel contact is necessary for GRF attenuation during gait. Since larger PIF and ALR have been linked to cartilage degradation in individuals with knee pathologies, the current results emphasize the role of quadriceps dysfunction in KOA development following ACLR. Improving quadriceps RTD may reduce loading characteristics that negatively influence cartilage health.