http://www.niams.nih.gov/Health_Info/Osteonecrosis/default.asp
National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health
This fact sheet provides answers to questions about osteonecrosis, a disease resulting from the temporary or permanent loss of blood supply to the bones. The fact sheet includes information on what osteonecrosis is, what causes osteonecrosis, and who is likely to develop osteonecrosis.