The influence of four-bar linkage knees on prosthetic swing-phase floor clearance

Four-bar linkage knees provide greater toe clearance during the swing phase of walking than do single-axis knees. The authors developed a computer model of a transfemoral prosthesis that allowed the kinematics of commercially available four-bar linkage knees and a single-axis knee to be simulated so leg-shortening could be characterized. A plot of hip-toe distance versus knee-flexion angle demonstrated four-bar knees are able to shorten the limb with less knee flexion than is needed using a single-axis knee. For a hip-knee angle combination at the time of minimum toe clearance during normal walking, contour plots revealed the four-bar knees have 0.9-3.2 cm greater toe clearance than do single-axis knees.