[Morphology of articular cartilage in fab2-induced arthritis of the knee-joint in the rabbit (author's transl)].

An arthritis closely resembling rheumatoid arthritis in man can be produced by the intra-articular injection of Fab2 into the knee joint of rabbits. This experimental model was used for the examination of ultrastructural alterations in articular cartilage. The lesion starts at the surface and advances gradually to the deeper zones of the cartilage. Morphologically, the lesion is characterized by progressive necrobiosis of the chondrocytes, as well as by a continually increasing thickening of the collagen fibres. It is suggested that the initial damage to the cartilage is not brought about by the pannus tissue, but is caused by a direct reaction to the pathologically-altered synovial fluid in response to inflammation.