In the study Contribution of Prosthetic Knee and Ankle Mechanisms to Swing-Phase Foot Clearance, published in a recent issue of Neural Systems and Rehabilitation Engineering, researchers analyzed toe clearance during prosthetic swing phase as a contributing factor in the likelihood of falls for transfemoral prosthesis users. The researchers concluded that four-bar knees provide greater foot clearance during prosthetic swing phase than single-axis knees, but that two currently available prosthetic ankle mechanisms with dorsiflexion during the swing phase provide significantly more clearance.
For data collection, researchers fitted ten people with transfemoral amputations with either single-axis or four-bar knees, and measured toe clearance during prosthetic swing phase from each trial. Two currently available prosthetic ankle mechanisms with dorsiflexion were modeled, and three-dimensional swing-leg simulations were used to differentiate between toe clearance attributed to knee mechanisms and those produced by compensatory gait differences.
According to the researchers, the data demonstrated that single-axis knees provided toe clearance of 4.6 cm during prosthetic swing phase, followed by four-bar knees at 5.8cm, and the two ankle mechanisms at 6.4cm and8.7 cm.