Adjustable Polycentric Mechanism for External Knee Joint Prosthesis Based on the Instantaneous Center of Rotation

The present study aims to develop a prototype of an adjustable knee prosthesis based on the Instantaneous Center of Rotation (ICR) of a set of commercial prostheses. The purpose is to improve user adaptation and approach natural kinematics. To develop this mechanism, some commercial prostheses are analyzed to obtain the trajectory of the CIR during angular displacement. Based on the different curves obtained for each prosthesis, a configuration of elements is proposed to approach the desired trajectories. The knee joint is designed and simulated with this basic configuration, and a rapid prototype is developed to validate its correct operation. The results show that the proposed adjustable mechanism can improve the adaptation of external knee prostheses to the user and approach natural kinematics.