Angular damping coefficient of the in vivo human knee joint.

multiplying the damping coefficient
by the angular velocity of the leg
(in rad/s). For example, if the
angular velocity is 10 rad/s the
passive viscous moment at 10º
would be about 13 N.m. Sincel the
small oscillation method is a linear
approximation, the values of the
damping coefficients presented in
this study probably represent the
upper limits since at higher
velocities the viscosity of the
passive tissues decreases due to the
nonnewtonian (thixotropic)
characteristics of biological tissues
and fluids (Fung, 1981).
In summary, the passive
moments which arise due to the
viscosity of the knee joint may be
significant in magnitude especially
for movements in which the knee
joint approaches its limits and the
magnitude of the net joint moment
is relatively small - such as during
the late swing phase of gait. If a
portion of the observed net joint
Figure 1. Mean angular damping coefficient of
the knee joint as a function of joint angle.
Dotted lines are ± 1 S.D.
moment could be satisfied passively, this will have implications in the magnitudes of the
predicted muscle forces.
REFERENCES
Davy, D.T., and Audu, M.L. (1987). Journal of Biomechanics, 20(2), 187-202.
Fung, Y.C. (1981). Biomechanics: Mechanical Properties of Living Tissues. New York:
Springer-Verlag.
Hatze, H. (1975). European Journal of Applied Physiology, 34, 217-226.
Hatze, H. (1975a). Ph.d. Thesis. University of South Africa.
Hatze, H. (1976). Mathematical Biosciences, 28, 99-135.
Winter, D.A. (1990). Biomechanics and Motor Control of Human Movement (2 nd ed.).
New York: John Wiley and Sons.
ACKNOWLEDGEMENTS
This study was partly funded by the Natural Sciences and Engineering Council and
the Research Committee of the University of Ottawa.