Early Stance Negative Knee Joint Powers and Knee Flexion Moments Can Be Tracked Using Inertial Measurement Units

Joint kinetics (e.g., moments and powers) are important markers of mobility and joint health but their measurement is generally limited to lab settings. However, we may be able to estimate kinetics with portable inertial measurement units (IMUs) by detecting important movement features that contribute to or occur simultaneously with kinetics. This study aimed to investigate whether early stance segment and joint angular velocities measured with IMUs correlate with early stance negative knee joint power and knee flexion moments. We collected motion capture, force plate, and IMU data during gait for healthy young adults, older adults, and older adults with knee OA. Peak knee flexion moments and early stance negative knee joint powers were calculated from motion capture data using inverse dynamics. Segment (thigh and shank) and joint (knee) angular velocities were calculated from IMU gyroscope data, and peaks in the first 5-25% of stance were identified. Pearson correlation coefficients were evaluated between motion capture data (peak knee flexion moments and negative knee joint powers) and IMU data (peak thigh, shank, and knee angular velocities). Significant correlations were found between negative knee joint powers and shank and knee joint angular velocities (r=0.59, p<0.001; r=- 0.37, p= 0.004, respectively). Knee flexion moments significantly correlated with shank angular velocities (r=-0.44, p<0.001). Our results suggest the potential to track longitudinal changes in knee joint power outside the lab with only a shank sensor.