The biomechanics of below-knee prostheses in normal, level, bipedal walking.

H U M A N locomotion involves the transformation of a series of controlled and coordinated angular motions occurring simultaneously at the various joints of the lower extremity into a smooth path of motion for the center of gravity of the body as a whole. Though largely taken for granted, it is an extremely complicated process, the complexity becoming evident when one considers that the path of motion is influenced by six major factors: knee-ankle interaction, knee flexion, hip flexion, pelvic rotation about a vertical axis, lateral tilting of the pelvis, and lateral displacement of the pelvis. A thorough study of walking in the orthograde attitude would therefore include not only the influence of each of these factors on the total displacement pattern but also a complete analysis of the action of major muscle groups of the lower extremity. The present discussion is limited to a consideration of the hip, knee, and ankle joints and of their interaction during level walking—first in the normal person and then in the case of the below-knee amputee wearing the patellar-tendon-bearing prosthesis with and without additional impedimenta in the form of thigh corset and sidebars.