Hip arthropathy in ochronosis: anatomical and radiological study.

Anatomical and radiological studies of four cases of ochronotic arthropathy of the hip were based on the examination of a total of six surgically removed femoral heads. One of these had undergone a surgical biopsy 10 years previously. The impregnation of the articular cartilage by the ochronotic pigment causes it to break into small fragments in the weight-bearing zone. This results in a similar osteoarthrotic remodeling to that commonly attributed to the histologically different "degenerative chondropathy". The labelling of the cartilage in ochronotic arthropathies offers an opportunity for better understanding of the main nonspecific components of osteoarthrotic remodeling. An anatomico-pathological approach explains why their radiological images in the hip may simulate those of rheumatoid arthritis.