Abstract
PURPOSE: Asymmetrical gait mechanics after anterior cruciate ligament reconstruction (ACLR) are associated with the development of posttraumatic knee osteoarthritis. Current measures of gait mechanics have focused heavily on peak magnitudes of knee kinematics, kinetics, and joint contact forces but have seldom considered the rate of knee loading, cumulative knee load, or the timing of motor input surrounding peaks. The purpose of this study was to introduce and describe novel metrics of gait using temporal characteristics of kinetics and EMG to identify neuromuscular deficits of the quadriceps in patients after ACLR. METHODS: Gait mechanics were assessed 6 months (n = 145) and 24 months (n = 116) after ACLR. External knee flexion rate of moment development (RMD) and knee flexion moment impulse (KFMI) leading up to the time of peak knee flexion moment (pKFM), peak RMD between initial contact to pKFM, and cumulative KFMI were calculated. Extensor latencies from the quadriceps, vastus medialis, vastus lateralis, and rectus femoris (time of pKFM - time of peak EMG activity) during the weight acceptance phase of gait were also calculated. Paired-sample t-tests (α = 0.05) were performed between limbs at both time points. RESULTS: Slower RMD, smaller KFMI, and longer extensor latencies in the involved compared with uninvolved limb were observed across all measures at 6 months (P < 0.005). At 24 months, RMDpeak was slower, and KFMI50ms, KFMI100ms, and KFMItotal were lower in the involved limb (P < 0.003), but no other asymmetries were found. CONCLUSIONS: Slower RMD, smaller KFMI, and prolonged extensor latencies may characterize neuromuscular deficits underlying aberrant gait mechanics early after ACLR. RMD, KFMI, and extensor latencies during gait should be considered in the future to quantify asymmetrical movement patterns observed after ACLR and as markers of recovery.