[Response of the joint tissues to the presence of a foreign body implanted into the rabbit knee. A new model of experimental arthrosis].

The joint tissues (synovium, articular cartilage and bone), respond rapidly and consistently to the presence of a piece of polypropylene surgically implanted into the Rabbit knee joint. In the contact of a foreign body, a synovium proliferates in an attempt to isolate and exclude the intruder from the joint cavity. The articular cartilage degenerates at the sites of maximal pressure. Its superficial layer undergoes cell necrosis and fibrillation and is progressively destroyed in the process of mechanical grinding. At the sites of lower pressure, the chondrocytes proliferate and form the metabolically hyperactive clones which have increased capacity to incorporate tritiated thymidine and radioactive sulfate. The glycosaminoglycan content of articular cartilage, compared to the shamoperated control side, rapidly decreases after operation as suggested by a loss of metachromatic staining and lower per unit weight concentration of uronic acid and hexosamine. In addition to the above changes, the osteophytes quickly develop at the articular margins from the proliferating synovial tissue while underlying bone become thicker and eburnated. These foreign body induced changes in articular morphology and metabolism resemble closely those observed in osteoarthrosis. The present model therefore may prove useful in studying the latter condition.