This study provides histological findings as to the pathogenesis of rapidly destructive coxarthrosis (RDC). Materials consisted of six femoral heads of RDC and several femoral heads of osteoarthritis and idiopathic avascular necrosis. According to histological findings, there were no changes in articular cartilage as in the cases of osteoarthritis or chondrolysis, but the most important findings were osteonecrosis of trabecular bone and invasion of synovia into the subchondral space of the femoral head. We suggest that the etiology of RDC is that the osteonecrosis may be intiated first and the absorption by synovia extended to the osteoporotic femoral head.
