For those DDH cases with mild pathological changes, it is difficult to find obvious abnormalities in clinical examination during the infant and toddler stage or even during the walking stage, and mainly rely on imaging examinations; for those DDH cases with more severe pathological changes, i.e. hip dislocation cases, it may be found that both lower limbs are unequal, i.e. the affected limb is shorter than the healthy limb; the thighs cannot be separated during diaper changing, etc. During the toddler stage, parents may notice that the child learns to walk later than his peers, one limb is shorter than the other, has a limp, and has an unstable gait. In bilateral subluxation, the child may have a “duck stance” with a pronounced posterior hip protrusion and increased lumbar protrusion. In adolescence, the child may experience weakness after exercise, back and hip pain, and even secondary osteoarthritis in the acetabulum, with gradually increasing pain and difficulty walking. Can the initial symptoms be recognized by the naked eye? For those cases of DDH with mild pathological changes, parents usually cannot recognize them with the naked eye because there are no obvious clinical symptoms, but need a specialist to recognize the abnormalities of imaging examinations with the naked eye. Even if the previously mentioned problems such as unequal length of both lower limbs and restricted hip division are found, they do not necessarily indicate DDH and need to be differentiated from other diseases. Abnormal gait after the walking period also needs to be differentiated from other diseases. In short, if parents find that their child has an abnormal gait, they need imaging to determine whether DDH is present, because the current understanding is that “symptoms” cannot be directly related to the diagnosis of DDH, which should be diagnosed on the basis of imaging. What are the effects of DDH on the growth and development of children in later stages? If DDH is detected, diagnosed and treated appropriately at an early stage, a normal hip joint can be obtained. If the diagnosis and treatment are delayed, even in those cases with relatively mild pathology, the pathological changes of the involved hip joint may continue to progress with time and walking, and complete dislocation of the hip joint may occur, or even degenerative changes of the hip joint may appear at an early stage, i.e. manifesting as symptoms such as limping and pain in the joint, affecting the patient’s quality of life. What bone and joint diseases can be triggered? If early detection, early diagnosis and early and appropriate treatment can be obtained, a normal hip joint can be obtained. If not diagnosed early and treated appropriately, the lesion may continue to progress until the hip joint is completely dislocated or degenerative changes in the hip joint occur early. This not only severely affects walking gait, but can eventually lead to many late complications such as chronic hip pain, early onset osteoarthritis, gait abnormalities and limb shortening, among others. This will affect the patient’s daily activities and reduce the patient’s quality of life. When should DDH screening begin? As mentioned above, the key to the treatment of DDH is “early”. We recommend that screening of the hip joint be started in the neonatal period if possible. At present, the examination methods for DDH are mainly physical examination and imaging examination, among which the diagnosis of DDH is based on imaging examination results, while physical examination can provide valuable reference for the diagnosis. The question of “early” is relative to “late”, but according to the current understanding and technology, how “early” can make an appropriate diagnosis, how “late” is a delay in diagnosis? According to the current tools available, hip ultrasonography can be performed after birth, but according to Graf’s method, a more definite diagnosis can only be made at 3 months of age after full-term birth. It is important to take full advantage of this time frame to differentiate between well-developed and abnormal hips.