Developmental Dysplasia of the Hip (DDH) is a common osteoarthritic deformity in children. It is a developmental abnormality of the hip joint that occurs at birth and continues to deteriorate after birth. If not diagnosed and treated early, the lesion will continue to progress until the hip joint is completely dislocated or degenerative changes in the hip joint occur early, which will seriously affect people’s walking gait and eventually lead to four major late complications: chronic pain, early osteoarthritis, gait abnormalities and limb shortening, which will affect people’s daily life and reduce their quality of life. In a normal person, there is a hip joint between the femur and the pelvis, and the femoral head moves within the hip joint, resulting in a casual and natural walking posture and flexible thigh flexion and extension. When the hip joint is dislocated, the femoral head cannot stay inside the joint normally and slips outside the joint, thus losing the normal anatomical relationship and affecting the normal functional activities of the lower limbs. Due to the different degrees of dislocation, developmental hip dislocation can be divided into: 1) complete dislocation; 2) semi-dislocation; 3) simple hip dysplasia, i.e., it mainly shows that the top of the acetabulum is more inclined and can develop into complete dislocation or semi-dislocation. Research results show that more than 50% of people with hip dislocation will have early degenerative changes in the hip joint into adulthood, and even require hip replacement. The key to the diagnosis and treatment of DDH is early diagnosis and early application of the correct treatment. The earlier the diagnosis, the easier the treatment and the safer and more effective the outcome. In 1927, Putti, an Italian orthopedic surgeon, said about congenital hip dislocation that “we should try to diagnose the disease at an early stage rather than designing a complicated surgery to solve it. “We should try to diagnose it at an early stage rather than designing a complicated surgery to solve it. This shows that doctors have long emphasized the importance of early diagnosis. According to preliminary statistics, most of the patients with DDH in infancy and early childhood can obtain a hip with near-normal anatomical relationship through correct and effective treatment; however, children older than 2 years old, even with correct treatment, may still develop residual hip deformity and early osteoarthritis. In general, early conservative treatment can last until about 2 years of age, surgical treatment is usually desired until 6 years of age, and unilateral lesions can extend the age of treatment to 8 to 10 years, but as age increases and secondary lesions worsen, it becomes more difficult to treat and ensure efficacy. So, how can we achieve early diagnosis? First, we need to recognize the disease.DDH is a multifactorial disease, including genetic factors and environmental factors. For example, endocrine factors, genetic factors, or some factors during birth (such as fetal position), etc. can cause poor hip development and eventually dislocation. Secondly, careful observation is needed. From the phenotype of infants and children, we can sometimes find popping in the hip joint, inconsistent length of the two legs, poor mobility and flexibility of one leg, asymmetrical skin pattern of the two legs, inconsistent hip-sharing activities of both legs, or other deformities, such as myotonic plagiocephaly and clubfoot. These high risk factors above need to be taken seriously by the family members, and once they are found to be in doubt, they need to consult a specialist in time to get early diagnosis and treatment. Most importantly, the development of imaging has provided us with effective tools for early diagnosis. Ultrasound, with its physical property of penetrating cartilage, is an effective means of demonstrating the unossified hip structures in the newborn and young infant period. In the diagnosis of developmental hip dislocation, ultrasound is able to detect signs of hip dislocation much earlier than the currently used radiographic methods. In children younger than 6 months, especially those younger than 4 months, ultrasound clearly demonstrates the advantages of imaging and reduces the risk of ionizing radiation in infants and children. Professor Graf, the originator of hip ultrasonography, reviewed and analyzed the follow-up of Austrian physicians after applying ultrasound to screen the hip, and the rate of hip dislocation surgery dropped from 3.5 per 1,000 in the 1990s to 0.13 per 1,000 at present, thus showing that the application of ultrasound coupled with proper early treatment has greatly reduced the posterior deformity of the hip and reduced the application of hip surgery. Early management after birth is the first line of defense to stop hip dysplasia from developing into late posterior deformity, and ultrasound provides valuable information at this stage to obtain a normal hip joint after proper treatment, so we call ultrasound the messenger to eradicate hip dislocation in children. Today, community physicians and parents are paying attention to the early diagnosis of hip dislocation and want their children to receive early and correct diagnosis and early and effective treatment. Hip ultrasound is increasingly refreshing the perception of hip dislocation diagnosis and treatment.