Osteonecrosis, also called avascular necrosis or aseptic necrosis, is a condition in which the death of bone cells (due to decreased blood flow) can lead to pain and collapse of areas of bone. This collapse of bone, in turn, can lead to degenerative arthritis of nearby joints, most commonly the hips and knees. Less frequently affected are the shoulders, hands, and feet. In rare instances, osteonecrosis can occur in the jaw— resulting in pain and mouth ulceration. Osteonecrosis is not fatal, but can lead to pain, arthritis, problems with physical activity, and even the need for joint replacement. Most of the 10,000 to 20,000 Americans developing osteonecrosis annually are between age 20 and 50. These individuals usually have a history of serious trauma, corticosteroid use, excess alcohol intake, or other conditions including systemic lupus erythematosus, dysbarism (“the bends” that occur with scuba diving), blood disorders, HIV infection, and radiation therapy.