Degenerative lesions were induced in the knee joint of Wistar rats by intraarticular injection of chondrocyte metabolism inhibitor mono-iodoacetate (MIA) at doses of 0, 0.3 or 3 mg/joint. Histopathological examination and the measurement of hind paw weight ratio as an index of joint pain by incapacitance tester were performed. Histological findings that are similar to those observed in human osteoarthritis (OA), such as disorganization of chondrocytes, erosion and fibrillation of cartilage surface, and subchondral bone exposure etc., were observed in a MIA-dose-dependent manner. Saflanin-O fast green staining revealed that marked diffuse reduction of proteoglycan in cartilage tissue of rats treated with MIA. The clinical scores of the joint pain were closely correlated to the grade of histological findings. We conclude that the present experimental model in combination with a novel dual channel weight averager would be very useful for the study of human OA, and could be applied for estimation of therapeutic effect of new anti-OA drugs.