Significance of connective tissue proliferation in the breakdown of cartilage: a novel in vivo model.

The implantation of homologous femoral head cartilage in subcutaneous tissues of random bred Wistar rats results in both subchondral and articular surfaces becoming overlaid by an adherent granulation tissue comprising predominantly fibroblast-like cells. The response of the tissue to cartilage encapsulated with cotton fibres was also similar but erosions, mainly subchondral, were more evident and proteoglycan loss markedly greater. The connective tissue response to cotton was the progressive formation of a foreign body granuloma comprising mononuclear cells, multinucleated giant cells, and fibroblasts with very few polymorphonuclear leucocytes.