A passive transfemoral prosthesis with movable ankle for stair ascent

Stair ascent is still a difficult task for transfemoral prosthesis users. So far, a passive knee joint unit for transfemoral prosthesis developed in our previous study achieved stair ascending without handrails or any other assistance devices. However, the experimental results with the simulated socket showed that the users faced difficulty in using the knee joint at the beginning of the load response phase. In addition, large moment power of the prosthetic side's hip joint in the stance phase was required, leading to a significant imbalance of power consumption between the intact and prosthetic sides. Therefore, the purpose of the present study was to develop a passive transfemoral prosthesis for stair ascent, which had a knee extension function associated with a movable ankle joint during the stance phase in order to change the admissible force region. Experimental results by nonamputated participants with the simulated socket demonstrated that ascending was achieved in the step-over-step manner without any assistive device. In addition, it was shown that the hip joint moment power reduced to equalize the joint moment powers in both sides.