Diagnosis and management of the osteonecrotic triad of the knee.

Generalized osteonecrosis of the knee may include, in addition to osteonecrosis of the medial femoral condyle that occurs most frequently, osteonecrosis of the patella or the tibial plateau. Such involvement is known as the osteonecrotic triad of the knee. Although the clinical picture of idiopathic osteonecrosis of the medial femoral condyle seems similar to several other disorders, certain distinct features, including its typical location,clinical symptoms, and late onset of cartilaginous erosion, facilitate differential diagnosis. Despite the progress made in the diagnosis and treatment of idiopathic osteonecrosis of the medial femoral condyle, the prognosis remains severe. More than 80% of the patients deteriorate to the extent that surgical reconstruction is necessary, whereas only about 20%of the patients demonstrate spontaneous resolution or no additional deterioration of the osteonecrotic lesion.