Prosthetic Knee for Transfemoral Prosthesis

This project involves the conceptual design, development and testing of a Polycentric Knee joint for persons with Transfemoral (above-knee) amputation. Also referred to as a "four-bar" knee, it has advantages over a hinge joint because of the multiple axes of rotation. The knee provides stability during the early stance phase of walking, yet is easy to bend to initiate the swing phase or to sit down. The four-bar knee causes the leg's overall length to shorten reducing the risk of stumbling. While the concept of a polycentric knee has been around for a long time in western countries, this aims to be the first indigenously designed knee from first principles (Prof. Radcliffe's seminal work), specifically optimized for users who have to navigate uneven terrain. The geometry is obtained by optimization based on certain hypotheses derived from literature and its suitability will be verified by clinical trials. The Instant Centre (IC) curve of this knee is markedly different from other commercially available knees.

The initial clinical trial conducted at Mobility India was very promising. The user was able to immediately recognize the stable nature of the knee. Despite having a very short residual limb to control the prosthesis, he was able to leave the safety of the parallel bars and take on open spaces in the initial trial itself. The knee also performed well while going up and down a ramp.

The knee design was the M. Tech project of T S Anand (2013-14) and was funded by the Society for Biomedical Technology (SBMT). We are working on design refinements and multiple prototyping to try the knee unit on users with different residual muscle capabilities. We also intend to perform a gait analysis to quantitatively evaluate the design.