Adult dysplasia of the hip (DDH congenital hip dislocation), is a relatively common clinical condition. It is mostly the result of missed diagnosis, delayed treatment or improper treatment due to insufficient awareness of such diseases in childhood. Because of the complex pathogenesis and pathological changes, the following issues should be noted in choosing the timing of artificial joint replacement: 1. Is the diagnosis clear? The differential diagnosis of hip dysplasia varies slightly due to differences in the level of diagnosis. It is important to correctly distinguish congenital from acquired, and whether it is associated with other diseases; to provide a detailed medical history, and to provide descriptions of different periods. Generally speaking, taking orthopantomogram of the pelvis and lateral radiographs of the affected hip can solve the problem initially; if allowed, 3D CT reconstruction of the hip joint is feasible to better understand the changes of the acetabulum and femoral head. In clinical work, most patients only provide the results of MRI examination when they visit the clinic, and ignore the role of plain X-ray in diagnosis. 2.Is it surgical treatment? Once hip dysplasia is diagnosed, it should be treated surgically in principle. Through pelvic osteotomy, femoral osteotomy and other methods to improve the inclusion and concentric relationship. However, adult cases are more complicated, and it is difficult to make up one’s mind in a short period of time because of age, disease duration, treatment methods and so on. Furthermore, most patients, regardless of their age, present to the clinic with pain as the main symptom and therefore, in theory, miss the opportunity to treat the osteotomy once it is done. To emphasize one point: age should not be a contraindication for osteotomy. In clinical work, hip dysplasia hip pain often heralds the beginning of osteoarthritis and gradually moves towards aggravation. If the pain can be relieved with rest or without weight-bearing, it can be treated by reducing weight and reducing weight-bearing on the hip joint. 3.Whether to perform artificial hip replacement? It has been proved that artificial hip replacement is a very effective treatment for adult hip dysplasia, and even the most serious cases of high dislocation (CROWE VI) can be treated as expected due to the continuous improvement of prosthesis design and surgical techniques. Therefore, after a clear diagnosis, if the patient’s pain gradually worsens and radiographs suggest osteoarthritis or provoked femoral head necrosis, artificial total replacement should be chosen.