Design of a fully passive prosthetic knee mechanism for transfemoral amputees in India

An estimated 230,000 above-knee amputees are in need of prosthetic devices in India with a majority of them facing severe socio-economic constraints in their daily lives. However, only a few affordable, passive prosthetic knee devices in the market have been designed to enable normative gait and to meet the unique daily life needs of above-knee amputees in the developing world. This paper builds upon our past study, which established optimal mechanical component coefficients in prosthetic knee function required for achieving able-bodied kinematics. We present a mechanism for the design of a fully passive prosthetic knee device, which aims to facilitate able-bodied kinematics at a low metabolic cost. The mechanism is implemented using an automatic early stance lock for stability, a linear spring for early stance flexion-extension and a differential friction damping system for late stance and swing control. For preliminary validation of the knee mechanism, we carried out a field trial on two above-knee amputees in India, which showed satisfactory performance of the early stance lock and enabled smooth stance to swing transition by timely initiation of late stance flexion.