Proximal powered knee placement: a case study

TL;DR

This study explores above-knee placement of powered prosthetic knees, showing potential for improved walking speed and gait mechanics, emphasizing the importance of mass distribution in prosthetic design.

Contribution

It demonstrates the feasibility and benefits of above-knee powertrain placement, highlighting the significance of mass distribution for optimizing prosthetic performance.

Findings

Above-knee placement improved walking speed (+9.2%) and cadence (+3.6%).

Gait symmetry effects were mixed across configurations.

Control strategy was robust across various locomotion tasks.

Abstract

Lower limb amputation affects millions worldwide, leading to impaired mobility, reduced walking speed, and limited participation in daily and social activities. Powered prosthetic knees can partially restore mobility by actively assisting knee joint torque, improving gait symmetry, sit-to-stand transitions, and walking speed. However, added mass from powered components may diminish these benefits, negatively affecting gait mechanics and increasing metabolic cost. Consequently, optimizing mass distribution, rather than simply minimizing total mass, may provide a more effective and practical solution. In this exploratory study, we evaluated the feasibility of above-knee powertrain placement for a powered prosthetic knee in a small cohort. Compared to below-knee placement, the above-knee configuration demonstrated improved walking speed (+9.2% for one participant) and cadence (+3.6%), with mixed effects on gait symmetry. Kinematic measures indicated similar knee range of motion and peak velocity across configurations. Additional testing on ramps and stairs confirmed the robustness of the control strategy across multiple locomotion tasks. These preliminary findings suggest that above-knee placement is functionally feasible and that careful mass distribution can preserve the benefits of powered assistance while mitigating adverse effects of added weight. Further studies are needed to confirm these trends and guide design and clinical recommendations.