Developmental Dysplasia of the Hip (DDH) is a disease in which the acetabulum does not cover the femoral head due to defective development of the acetabulum, resulting in long-term biomechanical abnormality and gradual development of subluxation of the femoral head, degeneration of cartilage in the weight-bearing area, focal cystic degeneration of the femoral head, and severe osteoarthritis. The main pathological changes are the defect of the acetabulum in the upper and anterior part of the acetabulum, the acetabulum becomes shallow, and the center of the hip joint moves outward, resulting in insufficient inclusion and coverage of the acetabulum to the femoral head.DDH can be accompanied by different degrees of subluxation of the hip joint. Due to the reduced coverage of the acetabulum over the femoral head, the relationship between the acetabular and femoral joint surfaces is not normal, which finally leads to increased contact stress on the joint surfaces and degeneration of the articular cartilage causing osteoarthritis of the hip joint. The disease has no obvious symptoms in the early stage, with the prolongation of time, mostly between the ages of 20 to 40 will produce symptoms. Initially, it manifests as soreness and discomfort in the hip, which is aggravated by prolonged standing or walking for a long time, and improves after rest. Later, hip pain gradually appears, mainly in the thigh root and groin area, sometimes accompanied by knee pain. There is no obvious obstacle to hip joint activity in the early stage. It is worth noting that pain in the hip joint often means that the cartilage of the hip joint has been damaged. The severity of hip joint pain is related to the degree and scope of articular cartilage damage. As the disease progresses, the pain in the hip joint further worsens and the movement of the hip joint is affected, with patients often having to use crutches to walk. If the symptoms appear at a younger age, it indicates that the degree of acetabular dysplasia is more severe. The prognosis is also worse. Symptoms are usually characterized by a sharp, cutting pain in the groin area, which is aggravated by prolonged sitting or walking. Activities that cause the hip to flex and internally rotate, and rapid descending of stairs, especially rotating stairs, can cause pain in the joint. In patients who lack anterior coverage of the femoral head there is often a dull popping sound when moving the joint. When the lower extremity is externally rotated, the tense iliopsoas tendon, sliding over the prominent femoral head, produces a painless and dull popping sound. This sign disappears with internal rotation or when the lower extremity is placed in a neutral position. In most patients, the clinical presentation is associated with underlying acetabular labral damage.