MATHEMATICAL-MODEL OF THE LOWER-EXTREMITY JOINT REACTION FORCES USINGKANES METHOD OF DYNAMICS

This report describes a new mathematical model for defining the joint reaction forces of the lower extremity using Kane's method of dynamics . Our model utilized average lower extremity joint motion and force/pl ate data from one healthy female patient during gait. From a cadaver s pecimen, the anatomical mass centers of the pelvis, femur, tibia, and foot were determined. Joint angular motion during the normal gait cycl e was computed using Cardan angles for each distal segment relative to the proximal segment. Fluoroscopy of four normal knees determined ave rage femorotibial and patellofemoral contact positions throughout flex ion. A three-dimensional model of the lower extremity was defined in w eight-bearing motion by 30 differential equations. During normal walki ng, the joint reaction forces for the subject tested ranged from 1.9 t o 2.6 times body weight at the hip joint and 1.7-2.3 times body weight at the knee joint, depending primarily on gait speed. The method corr elates well with known in vivo telemetrically measured forces at the h ip joint. (C) 1998 Elsevier Science Ltd. All rights reserved.