Osteonecrosis, also known as avascular necrosis, is a condition in which bone tissue dies due to a loss of blood supply. Without adequate circulation, the affected bone weakens and may collapse over time, leading to joint pain and impaired movement. It most commonly affects weight-bearing joints such as the hip, knee, or shoulder. Causes can include trauma, long-term use of corticosteroids, excessive alcohol consumption, blood clotting disorders, or certain medical treatments, though sometimes no clear cause is identified. Early stages may produce mild or no symptoms, but as the condition progresses, pain typically increases and joint function declines. If untreated, osteonecrosis can lead to joint destruction and the development of arthritis.