Stage 0: The hip joint is asymptomatic and the radiographs are not abnormal, but because the opposite side is already symptomatic and diagnosed, and more than 85% of the patients are affected bilaterally, the gang calls this stage the silent hip, in fact, at this time, isotope scan, intraosseous pressure measurement or marrow core biopsy have proved that there are changes, and this is a good time for decompression treatment. Stage I: Pain at the hip joint, which may occur after trauma or exertion, is progressive, heavy at night, and slightly limited in internal rotation and abduction. x-ray films show that some areas are sparse, with positive pressure measurement and biopsy. Decompression therapy is more effective in this stage. Stage II: The clinical symptoms continue to worsen, and the X-ray shows increased bone density and cystic changes, and the subchondral bone appears as an arc-shaped translucent band, called the crescentic sign, but the femoral head is still normal in shape. Stage III: The pain of the diseased hip hinders the movement, and the activities of all parties have been significantly limited. The edge of the femoral head on X-ray has overlapped due to collapse, or has lost its round shape, and the sclerotic area is obvious. Although the diagnosis is easy to determine, the management is difficult. Stage IV: The disease has reached an advanced stage, with deformation of the femoral head, narrowing of the joint space, sclerosis of the acetabulum, and obvious signs of osteoarthritis.