Development of a passive mechanism of transfemoral prosthetic knee for running without falls

Abstract

Transfemoral prosthesis users are easy to fall during running because prosthetic knees for running do not have flexion lock function during stance phase. Therefore, the purpose of the present study was to propose a passive mechanism of transfemoral prosthetic knee to prevent unintended knee flexion during running. The proposed mechanism has a single axis for prosthetic knee flexion–extension. Knee flexion lock function was realized with the force on knee joint along the long axis of the shank part (ground reaction force), and we showed statics of the mechanism of the function. The mechanism limits only flexion and allows extension during the stance phase. During the prosthetic swing phase, it rotates flexion and extension. These functions of the proposed mechanism were verified using a rough prototype. The intact participant with a simulated thigh socket and the prototype performed level walking. As a result, when teeth of the spur gear and stopper in the mechanism were engaged, the knee joint produced extension moment without knee flexion as we designed. Smooth flexion and extension of the prosthetic knee were observed during the swing phase.