Subchondral avascular necrosis: a common cause of arthritis.

(1) Subchondral avascular necrosis is an important cause of joint pain and disability and accounts for upwards of 20% of total hip replacements done in our hospital. (2) Early diagnosis may be made with the aid of magnetic resonance imaging and radioactive isotope studies. (3) Although the signs and symptoms are similar to those of osteoarthritis, there are significant differences--namely, (a) a history of sudden onset of pain, present in more than half the patients; (b) a younger age group; (c) a shorter duration of symptoms at time of surgery; (d) clinically the limiting factor is pain rather than actual joint deformity to account for restriction of movement; (e) a high incidence of multiple sites of involvement. (4) The disease is commonly associated with steroid treatment or alcohol abuse. Although many other causes are recognised, they are rare in Western urban practice. (5) Patients with stage I-II subchondral avascular necrosis, especially of the knee, are better treated conservatively. (6) Surgical treatment gives less satisfactory results than the treatment of osteoarthritis by similar modalities.