1.What is DDH DDH is a congenital developmental disorder of the hip joint, the hip joint is a mortar and pestle joint, DDH acetabulum shallow small, the femoral head that is slipping out of the socket, can be partially or completely dislocated. The incidence is about 1/1000. 2, the causes of DDH hip dislocation is caused by many reasons, including genetic and environmental, family history of developmental hip dislocation or ligamentous laxity, intrauterine fetal position, especially the breech position. 3.What are the symptoms of DDH including: the leg on the dislocated side is shorter than the other side, the leg on the dislocated side is externally rotated, the skin folds on the thighs or hips are asymmetrical, and the distance between the two legs is larger than normal children. 4.Diagnosis of DDH Neonatal physical examination screening, X-ray, ultrasound, CT, MRI 5.Treatment of DDH: Children: children within 6 months wear Pavlik brace to make the hip position normal, during this period, we should often take the child to follow up to check whether the brace is worn properly and check the hip joint condition. At the end of treatment, an X-ray (or ultrasound) will be taken to check the position of the hip joint. It is possible that the child can be successfully treated with a Pavlik brace, but in some cases there may be partial or complete dislocation. If there is still a partial or complete dislocation, traction, a cast or surgery will be required. If the child is older than 18 months of age at the time of DDH, surgery will be performed to put the hip joint into a normal position, i.e., a closed reposition. Adults: If the joint is functioning well, reduce weight-bearing activities. If the function of the joint is poor and affects normal life, surgical treatment including osteotomy or artificial joint surgery should be considered.