Generally occurs after a temporary or permanent loss of blood supply to bones.
Postulated mechanisms for its development include fat embolism, a vascular thrombosis, and osteocyte apoptosis.
Incidence among patients who take glucocorticoids estimated to be between five and 40% with increased risk among patients with higher doses and prolonged exposure, although it may occur with short-term exposure to high doses.
Intra-articular glucocorticoids (usually methylprednisolone) may cause osteonecrosis of bone.
Frequently caused by radiation or combined chemoradiation especially for head and neck cancers.
Non malignant causes include trauma with blood vessel injury that supply the bone, obstruction of blood flow by air, fat or clots, hypercoagulative states and vasculitis.
Impaired blood supply leads to bone necrosis, dissolution of bone and lytic changes on bone x-rays or computerized axial tomography, and to localized bone collapse.
Symptoms include pain, stiffness, impaired mobility and associated muscle spasm.