A Study of Tibial Motion Accuracy using Circular and Noncircular Gears in a Transfemoral Prosthetic Knee Part 1: Tibial Motion Acquisition

This is the first part of a two-part work where the authors' design method for gear-based transfemoral prosthetic knees is demonstrated using knee motion data from 7 clinical knee motion studies. The purpose of this two-part work is to determine if circular gears can consistently exhibit accurate tibial motion during gait versus noncircular gears in a transfemoral prosthetic knee. In part 1, tibial positions reflecting tibial motion during gait are calculated using the knee motion data presented in the 7 clinical knee motion studies. These studies reflect factors such as participant age, gender, nationality, body mass index, gait speed and knee condition. Unlike noncircular gears, which are custom-made, circular gears can offer advantages in manufacturing cost and design simplicity since it is a standard component. However, to justify the use of circular gears in the knee design, it must be determined if it can consistently exhibit tibial motion that is as accurate as noncircular gears.