The measurement of rabbit's knee friction with a pendulum friction tester

To investigate the friction of rabbit’s knee joint with designed pendulum friction tester to diagnose and evaluate different pathological and therapeutic conditions following haemarthrosis, osteoarthritis, and other joint disorders. Friction coefficient of 10 adult male Albino rabbit’s joint (5 right and 5 left knees) weighted 1.59 ± 0.27 Kg, after designing and compiling the instrument and its processing software in the Physiotherapy department of Tarbiat Modares University were measured. Maximaum pendulum rotation, number of oscillations to reach equilibrium, coefficient of friction with Stanton’s equation, exponential and linear curve fitting, average logarithmic and linear decrement methods were measured. Maximum rotation after pendulum releasing in the left joints were higher than the right ones, P<0.001. Number of oscillations to reach equilibrium in the left knees were also greater than the right knees, P=0.005. All different friction estimation methods had the same results and showed greater friction in the right in comparison to the left side. The pattern of the joints amplitude decay did not have a linear behaviour and the rabbit’s knee joint coefficient of friction with nonlinear estimations was less than linear ones. The findings revealed that selecting a separate control group in such investigation is essential and the contralateral limb could not be considered as control group. Pendulum friction tester has the capability of evaluating changes in coefficient of friction after application of different therapeutic methods. These changes have important role in diagnosis, evaluation of joint diseases and developing techniques for treating those pathologies.