Abstract
Stair ascent is still difficult for trans-femoral prosthesis users though stability of the prosthesis has been established in level walking. The purpose of the present study was to develop a passive knee joint unit of the prosthesis that enabled trans-femoral amputees to ascend stairs. The proposed knee joint unit had knee flexion function in swing phase as well as knee flexion lock and knee extension functions during stance phase. Stair ascent experiments demonstrated that the trans-femoral prosthesis with the proposed knee joint unit allowed stair ascending in the step-over-step manner without any assistive device. It was shown that knee extension moment and its positive power, which were unrealizable by the existing knee joint mechanisms, were realized in stance phase. In addition, the knee flexion in swing phase allowed the stair ascent without any collision with the stairs.
