A Magnetorheological Transfemoral
Knee Prosthesis

A magnetorheological knee prosthesis is developed that automatically adapts knee damping to the gait of the amputee, using only local sensing of knee force, torque, and position. To assess the clinical effects of the user-adaptive knee prosthesis, kinematic gait data were collected on four unilateral trans-femoral amputees. Using the user-adaptive knee and a conventional, non-adaptive knee, gait kinematics were evaluated on both affected and unaffected sides. Results were compared to the kinematics of 12 age-, weight-, and height-matched normals. We find that the user adaptive knee successfully controls early stance damping, enabling the amputee to undergo biologically realistic, early stance knee flexion. Additionally, the user-adaptive knee constrains the maximum swing flexion angle to an acceptable biological limit. These results indicate that a user-adaptive control scheme and local mechanical sensing are all that is required for amputees to walk with an increased level of biological realism compared to mechanically passive prosthetic systems.