Evaluation of EMG-Assisted and EMG-Driven control modes in patients with medial compartment knee osteoarthritis

Knee osteoarthritis (OA) is associated with higher-than-normal knee joint contact forces (KJCFs) during walking which cannot be easily measured. KJCFs can be estimated using neuromusculoskeletal (NMSK) modelling in electromyogram (EMG)-driven and -assisted control modes. Previous research has not examined which control mode is most appropriate for estimating KJCFs in patients with knee OA. This study aimed to evaluate a NMSK modelling framework using both control modes in patients with medial-dominant knee OA. First, EMG-assisted mode was hypothesized to better track ID-computed joint moments. Second, KJCFs estimated using the two control modes were hypothesized to differ. Gait data were measured from 27 patients with medial-dominant tibiofemoral knee OA. An OpenSim model was scaled to patient-specific anthropometrics. Inverse kinematics, inverse dynamics, and muscle analysis were performed. Resulting joint angles, moments, musculotendon kinematics, and muscle activations were input into the Calibrated Electromyography Informed Neuromusculoskeletal Modelling Toolbox. Muscle forces and KJCFs were estimated using EMG-driven and -assisted control modes. EMG-assisted mode better tracked knee flexion moments (RMSE = 2.7 ± 2.1Nm, R² = 0.9 ± 0.1) and estimated a higher, albeit non-significant, second peak medial compartment KJCF (2.3 ± 1.1BW) compared to EMG-driven mode (RMSE = 12.6 ± 3.9Nm, R² = 0.6 ± 0.2, KJCF = 2.1 ± 0.9BW). EMG-assisted control mode may therefore be more appropriate for evaluating KJCFs in patients with knee OA.