Avascular necrosis is a condition in which blood supply to the bone is lost leading to bone cell death, collapse, bone destruction, and may even lead to eventual joint dysfunction. The hip is the most common site of avascular necrosis, though it can attack any bone or joint. The only real symptom is pain. While avascular necrosis doesn't seem threatening from the outset, if left untreated, it can become very serious – in fact, at the first sign of bone pain, you should visit your doctor.  However, you can detect the symptoms and put a stop to it before serious treatment is necessary.