The development of the acetabulum is shallow and vertical, the head and socket are disproportionate, the femoral head is poorly inclusive, the head and socket lose the normal matching anatomical relationship, or even completely dislocate, which leads to biomechanical damage of the hip joint, accelerates the mechanical wear of the hip joint, prematurely causes hip joint degeneration, and leads to secondary hip osteoarthritis. 1, clinical manifestations The onset is insidious, most of the symptoms appear between 20 and 40 years old, more women than men (about 6:1), unilateral predominant; hip pain progressively aggravated, walking gait limp; hip joint asymmetry, limbs are not equal, thigh thickness is not equal; X-ray manifestations are steep and shallow acetabulum, subluxation, dislocation and joint space narrowing, osteosclerosis and other arthritic manifestations. 2.Typing is divided into four types according to the degree of dislocation Type I: the femoral head is not fully covered, but still located in the center of the mildly dysplastic acetabulum. Type II: the femoral head is still located in the center, but there is a significant lack of inclusion. Type Ⅲ: the femoral head is dislocated upward and laterally, the diseased acetabulum becomes shallow and flattened accordingly, and the CE angle is negative Ⅳ: complete hip dislocation, the femoral head is located at the outer edge of the acetabulum, and the affected limb is clearly shortened 3, arthritis progression stage Pre-stage: abnormal increase in acetabular angle, normal joint space, hardening of the weight-bearing area Initial stage: narrowing of the acetabular space, hardening of the weight-bearing joint surface, poor matching of the acetabulum and the femoral head Bone spur formation Progression stage: joint surface hyperplasia The joint space is obviously narrowed, the femoral head is displaced outward, the weight-bearing area is osteosclerotic and cystic. Late stage: the joint space disappears, the femoral head is collapsed, deformed, worn, displaced upward, and the lateral edge of the acetabulum is obviously hyperplastic and sclerotic. 4.Treatment Pre- and early stage: as the damage to the articular cartilage is not very serious, acetabular rotational osteotomy can be performed to increase the inclusion of the femoral head and achieve the time without joint replacement or delaying the artificial joint replacement surgery. Progressive and late stage: the articular cartilage damage is serious, and only artificial total hip replacement can be performed.