Induction of osteoarthrosis in the guinea pig knee by papain

The main purpose of this investigation was to develop a model for experimental induction of osteoarthrosis. A previously described method using papain was tried on guinea pig knee joints. Eighteen adult guinea pigs were given papain intra-articularly in the right joints; the left joints were used as controls. The animals were killed after 6 hours, 1 week, 2 weeks, 2 months, 4 months, 6 months, 8 months, and 10 months. Specimens of the articular cartilage were removed for histologic and histochemical investigation. Microscopic surface irregularities could be observed in the animals after 6 hours, 1 week, and 2 weeks, and again after 8 and 10 months. Histochemical examination of the sections from the experimental joints indicated a loss and degradation of the sulfated glycosaminoglycans. This loss was evident after 6 hours, 1 week, 2 weeks, and 8 months. The first osteoarthrotic changes were observed macroscopically after 8 months. Radiographic changes in the experimental joints could be observed in all animals killed after 10 months. It was concluded that osteoarthrosis similar to that occurring in humans can be induced by this method.