A detailed model of the human knee was developed to predict shank moti
on induced by functional neuromuscular stimulation (FNS). A discrete-t
ime model is used to characterize the relationship between stimulus pa
rameters and muscle activation. A Hill-based model of the musculotendo
n actuator accounts for nonlinear static and dynamic properties of bot
h muscle and tendon. Muscle fatigue and passive muscle viscosity are m
odeled in detail. Moment arms are computed from musculotendon paths of
13 actuators and from joint geometry. The model also takes nonlinear
body-segmental dynamics into consideration. The simulated motion is vi
sualized by graphic animation. Individual model parameters were identi
fied by specific procedures such as anthropometric measurements, a pas
sive pendulum test, and specific open-loop stimulation experiments. Mo
del results were compared with experimental data obtained by stimulati
ng the quadriceps muscle of paraplegic patients with surface electrode
s. The knee moment, under isometric conditions, and the knee angle, un
der conditions of freely swinging shank, were measured. In view of the
good correspondence obtained between model predictions and experiment
al data, we conclude that a biomechanical model of human motion induce
d by FNS can be used as a mathematical tool to support and accelerate
the development of neural prostheses. Copyright (C) 1996 Elsevier Scie
nce Ltd.