On the basis of recently published experimental results of Abramowitch et al. (2004), dealing
with viscoelastic properties of sham operated and healing MCL, we show that the fractional Zener
model of viscoelastic body seems to be very tractable tool for rheological description of different
states of biological tissues. In this paper medial collateral ligament of the knee will be described
by means of the method of Dankuc et al. 2010, who examined middle ear structures and ramp-and
hold stress relaxation experiments. Two different states of MCL were described by four different
constants representing modulus of elasticity, the order of fractional derivative and two relaxation
constants. Predictions of the model are in good agreement with the experimental results.