Involvement of the hips is an often-ocurring, and frequently disastrous complication of both rheumatoid and osteoarthritis. In these conditions early symptoms of hip joint difficulties are certain forerunners of serious deterioration. Involvement of one side often is followed by involvement of the other side and pain and disability tend to increase until walking and standing become impossible. Disabling arthritis of the hips may be encountered also as a late complication of other ailments, notably coxa plana, Legg's disease, slipped femoral epiphyses, aseptic necrosis of the femoral head, Charcot's disease of the hip, Paget's disease of the pelvic bones, fat embolism, and avascular necrosis of the femoral head subsequent to dislocation. Similarly, arthritis may develop in the hip following surgical treatment for fractures of the femoral head and neck. In some instances, the hip joint deteriorates without recognizable cause in persons with "dysplastic" or poorly formed pelvic bones. There is no