Effects of surgically induced instability on rat knee articular cartilage.

Degenerative lesions in the articular cartilage were present following transection of the anterior cruciate ligament in the rat. These lesions included surface disruptions, a reduction in matrix proteoglycans, and cellular changes and therefore were similar to lesions seen in dogs following transection of the anterior cruciate ligament as well as lesions seen in other mechanical derangement models. Lesions were more frequently encountered in animals that had been exercised on a treadmill. This suggests that the rat knee joint may be a useful small animal model in studying the effect of mechanical derangement on articular tissues.