Materials and Methods: 12 animal models of early stages of cartilage degeneration were established by intra articular injection of 10 units of papain causing a reversible loss of cartilage proteoglycan in dog knees.

• 材料与方法：选用健康家犬12条，在右侧膝关节腔内注射0.；2ml木瓜蛋白酶溶液（10U），可逆性地降解软骨内蛋白多糖基质，建立早期软骨退变的动物模型。