musculoskeletal and connective tissue disorders
Osteonecrosis (ON)
Key Points
Osteonecrosis is most often a complication of displaced subcapital femoral neck fracture, but factors that compromise bone blood flow (eg, sickle cell disease) increase risk of nontraumatic osteonecrosis. Osteonecrosis should be suspected in patients with unexplained nontraumatic pain in the hip, knee, or shoulder (sometimes the wrist or ankle) and after certain fractures if pain persists or worsens. Although x-rays may be diagnostic, MRI is more sensitive and specific. Smaller lesions may heal spontaneously, but most larger lesions, especially in the hip, progress without treatment. Nonsurgical treatments are not widely used because efficacies are not clearly proved. Surgical treatment is often indicated to limit progression and/or relieve symptoms, particularly for osteonecrosis of the hip. 