Osteonecrosis, also known as avascular necrosis, is a condition that occurs when blood flow to a bone is reduced or interrupted. This lack of blood supply can lead to the death of bone tissue, causing pain and potential joint collapse. It commonly affects the hip, knee, and shoulder joints. The condition can result from various factors, including trauma, long-term use of corticosteroids, excessive alcohol consumption, and certain medical conditions like lupus or sickle cell disease. Early diagnosis and treatment are crucial to prevent further damage and maintain joint function.