An experimental study on in vivo dynamic mechanical properties of the knees of cats in valgus loading

In these experiments an attempt was made to investigate in vivo dynamic mechanical properties of the knee in valgus loading. Fifteen adult cats were used. Sinusoidal bending oscillation of 0.3, 1.0, 1.6, 3.3, 5.0, 8.6 and 10.0 Hz was transmitted to the knee-leg complex under each pre-bending strain in the valgus direction, and the bending moment was measured. Dynamic mechanical properties of the knee-leg complex were given as a complex bending elastic coefficient. Bending elastic and bending damping coefficient of the knee could be calculated by the least square method. As a first approximation, the knee was represented as a non-linear Kelvin model. Both bending elastic and bending damping coefficient of the knee increased as pre-bending moment was increased, and decreased as amplitude of bending oscillation was increased. Mechanical loss tangent of the knee-leg complex decreased within the range of pre-bending moment larger than 1.0 X 10(6) dyn cm as bending moment was increased, and decreased as amplitude of bending oscillation was increased.