Jay, Gregory D., et al. Frictional Properties of Hartley Guinea Pig Knees With and Without Proteolytic Disruption of the Articular Surface. Osteoarth Cartilag 15:309-315, 2007.
This study applied a pendulum technique to detect changes in the coefficient of friction of the articular cartilage of the intact guinea pig tibiofemoral joint after proteolytic disruption. The study found that treatment with a-chymotrypsin induces mild cartilage surface damage and increases the coefficient of friction in the Hartley guinea pig knee.