(1) Clinical symptoms, signs and history: Arthralgia mainly in the groin, hip and thigh, occasionally with knee pain, limited hip flexion and internal and external rotation, often with a history of long-term heavy hormone use, hip fracture, alcoholism and occupational history such as diving and flying. (2) X-ray changes: in the early stage, there is an increase in density (sclerosis) and translucent area (cystic change); in the further development, there is a typical “crescent” change; in the late stage, there may be deformation and collapse of the femoral head and severe osteoarthritic changes, and there is sclerosis and cystic change in the acetabulum. (3) CT scan changes: sclerotic band surrounding necrotic and repaired bone in the femoral head, or subchondral bone fracture changes. (4) MRI: banded low signal in the necrotic area TlWI or double line sign in T2WI. (5) Bone scan: early perfusion defect (cold area) changes: as the disease worsens, “bagel-like” changes appear, that is, hot areas containing cold areas. (6) Bone biopsy: trabecular bone cells in the necrotic area are more than 50% of the trabecular bone cells, and the bone marrow is necrotic. Definitive diagnosis condition: two or more diagnostic criteria are met. （Any one of (2), (3), (4) and (6) is met.