Stage 0: bone marrow biopsy results consistent with femoral head necrosis, other items normal; Stage 1: positive nuclein or MRI; Stage 2: abnormal plain film (splotchy femoral head, osteosclerotic lines, cystic changes, little bone); no collapse indications on plain film or CT, positive nuclein, MRI, no changes in acetabulum; Zhao Baoxiang, Department of Orthopedics, Linyi People’s Hospital Stage 3: crescent sign, based on the location of the femoral head being invaded, can be divided into internal and external necrosis. Stage 4: flattening of the femoral head, narrowing of the joint space, sclerosis, cystic changes and bone redundancy in the acetabulum on plain film.