Estimation of Recommended Damping Coefficient Range to Achieve Target Peak Knee Flexion in a Passive Prosthetic Knee

There is a lack of predictive biomechanical models and publicly accessible empirical data that quantitatively explore the effect of damping magnitude on the peak knee flexion angle during the swing phase.

A three-step framework estimates a recommended damping coefficient range required to achieve able-bodied peak knee flexion during swing. A recommended damping range (0.29- $0.56\times {10}^{-2}[-]$ ) was estimated using experimental able-bodied gait data and adjusted based on expected walking speed and shorter duration of swing flexion common in transfemoral prosthetic gait. The resulting damping range was experimentally investigated with five transfemoral amputees. Knee kinematic data were collected from each person for five different damping coefficients that spanned a broad range of values, including the recommended range predicted by the framework.

The experimental study showed that the framework calculates an efficient starting damping value that promotes target able-bodied peak knee flexion. The damping coefficient values within the predicted recommended range resulted in able-bodied peak knee flexion (56 ± 3°) in the prosthetic leg for three out of the five participants. Increasing damping decreased the peak knee flexion, with the no-damping condition resulting in hyperflexion.

This framework could allow prosthetic knee designers to develop devices with near-optimal damping, which may increase efficiency for clinical tuning, especially in low- and middle-income countries, where controlled knee flexion is the desired outcome.