1.Pain. Pain can be intermittent or persistent, aggravated by walking activities, sometimes rest pain. The pain is mostly pins and needles, dull pain or soreness and discomfort, often radiating to the groin area, inner thigh, posterior hip and medial knee, with numbness in the area. 2.Joint stiffness and activity limitation. The affected hip joint flexes and extends unfavorably, has difficulty squatting, cannot stand for a long time, and walks with a duck walk. The early symptoms are limited abduction and external rotation activities. 3.Crippling. Progressive shortening limp, due to hip pain and femoral head collapse, or late onset of hip subluxation. Intermittent claudication often occurs in the early stage, and is more obvious in children. 4. Physical signs. Local deep pressure pain, pressure pain at the stop point of the adductor muscle, positive 4-character test, positive hip flexion contracture test, positive hip abduction and internal rotation test, positive gluteus medius test. There is limitation of abduction, external rotation or internal rotation, shortening of the affected limb, muscle atrophy, and even signs of subluxation. Sometimes the axial impulse pain is positive. 5.X-ray performance can be divided into 5 stages: stage 0 (pre-radiographic stage) about 50% of patients in this stage can have mild hip pain, which is aggravated by weight-bearing. X-ray shows that the hip joint may be negative, but scattered osteoporosis or blurred bone trabeculae can also be seen. At this stage, CT and MRI can be used for early detection. Stage I (pre-necrosis, head flattening) has obvious clinical symptoms and is worse than stage I. Radiographs show: extensive osteoporosis of the femoral head, scattered sclerosis or cystic changes, disorganized and interrupted bone trabeculae, some necrotic areas, and normal joint space. Stage II (migratory phase): clinical symptoms continue to worsen, radiographs show mild flattening of the femoral head, collapse within 2 mm, and mild narrowing of the joint space. Stage III (collapse phase) clinical symptoms are more severe. X-rays show that the external contour and trabeculae of the femoral head are disrupted and interrupted, with hemimelia, collapse greater than 2mm, dead bone formation, flattening of the head, and narrowing of the joint space. Stage IV (osteoarthritis stage) has clinical symptoms similar to osteoarthritis, with significant pain and severely restricted joint range of motion. x-ray shows: collapse of the femoral head, marginal hyperplasia, fusion or disappearance of the joint gap, and subluxation of the hip joint.