ABSTRACT
Osteonecrosis appears as a distinctive feature in a number of non-traumatic disorders: joint infection, Perthes' disease, caisson disease, Gaucher's disease, systemic lupus erythematosus (SLE), high-dosage corticosteroid administration and alcohol abuse. Various mechanisms leading to capillary thrombosis have been demonstrated in patients with non-traumatic osteonecrosis. Computed tomography (CT) involves considerable radiation exposure and it is not very useful for diagnosing osteonecrosis. Where risk factors for osteonecrosis are recognized, preventive steps can be taken especially in the management of corticosteroid medication and alcohol abuse. 'Spontaneous' osteonecrosis of the knee is similar to osteochondritis dissecans of the medial femoral condyle, but it is distinguished by three important features: it appears in elderly people who are osteoporotic and the lesion invariably appears on the highest part of the medial femoral condyle. Similar 'bone marrow oedema changes' are sometimes seen in areas around typical lesions of osteonecrosis.
