Abstract:
The most effective way to improve mobility and life quality following an amputation is by the
use of a properly designed prosthetic system. However, many amputees are priced out to
receive customized modern prosthetic services in Sri Lanka. This study is focused on
developing a resilient, homemade four-bar prosthetic knee with readily available two types of
Nylon material, Hard Nylon and Oil Impregnated Nylon, which are very affordable costing
approximately £29 per unit, and sustainable. Our four-bar linkage polycentric knee design has
several new advancements, to address the shortfalls of previous versions. Following the
biomechanics of the polycentric knee joints with 4 bar mechanisms, the link dimensions of this
model were designed specifically by, shortening the top linkage (25mm) and extending the
bottom linkage (40mm) subsequently raising the Instantaneous Center of Rotation and moving
it posterior to the weight line offering natural stability. These link dimensions were offered
18mm ground clearance. The geometric angle between the top linkage and the horizontal line
is optimized to 330 to enable effortless push-off without disturbing the stability. Adjustable top
and bottom attachments facilitate modifications to individual requirements. This model knee
autonomously depends on the muscle action of the residual limb to swing through during the
swing phase thus, avoiding inconsistency and unreliability of the braking action. In conclusion,
we have shown that there is scope for improvement in currently existing knees in terms of their
functionality and cost-effective production for developing countries and have designed a knee
that provides greater stability and toe clearance to better navigate uneven terrain. It is expected
to transfer the lesson learned from this study to future work including gait studies with prosthetic
users to evaluate kinematics, kinetics, and energy consumption, along with other gait parameters
through full-scale clinical trials to validate the results of this knee.
