A more informed evaluation of medial compartment loading: the combined use of the knee adduction and flexor moments

Abstract

To evaluate if the peak knee flexor moment (pKFM) provides unique and meaningful information about peak medial compartment loading above and beyond what is obtained from the peak knee adduction moment. Standard video-based motion capture and EMG recordings were collected for 10 anterior cruciate ligament (ACL) reconstructed subjects walking at a self-selected speed. Knee joint moments were obtained using inverse dynamics and medial contact force was computed using an EMG-driven musculoskeletal model. Linear regression with the peak adductor moment entered first was implemented to isolate the unique contribution of the peak flexor moment to peak medial loading. Peak moments and medial contact force occurred during weight acceptance at approximately 23% of stance. The peak knee adduction moment (pKAM) was a significant predictor of peak medial loading (P=0.004) accounting for approximately 63% of the variance. The pKFMwas also a significant predictor (P=0.009) accounting for an additional 22% of the variance. When entered together pKAM and pKFM accounted for more than 85% of the variance in peak medial compartment loading. The combined use of the peak knee flexor and adductor moments provides a significantly more accurate estimate of peak medial joint loading than the peak adduction moment alone. More accurate inferences of joint contact force will assist clinicians and researchers investigating relationships between joint loading and the onset and progression of knee osteoarthritis (OA).