A mathematical description is proposed of the relative motion at the human knee joint idealized as two dimensional. Based on the relatively few available measurements and the current anatomical literature, the problem has been the identification of the basic kinematic characteristics of this motion, recognizing the variation of human knees and locomotion. With the aid of the anlytical description of plane, relative motion in terms of centrodes and curvature considerations (Euler-Savary equation and related concepts). the basic kinematic characteristics of knee motion have been deduced and the shape of the simplest centrodes reproducing these characteristics described mathematically. Current above-knee and below-knee prostheses remain predominantly of the singlehinge or single-pin type. A knowledge of the shape of the centrodes defining the relative motion of a real human knee may, it is hoped, serve as a guideline in the mechanical design of anatomically more accurate prostheses. © 1968 N. Rashevsky.
