The so-called hip line asymmetry refers to the two sides of the inner thigh skin folds asymmetry; if there is a hip dislocation, often the affected side of the skin wrinkles deepening increase. More parents think it may be because of the child’s obesity, nothing serious. However, some parents brought their children to the hospital for a checkup, but was told that the child is a developmental hip dislocation. Developmental hip dislocation is the most common limb deformity. Children are born with a high rate of hip instability, but do not develop it completely. Generally high incidence of white people, black people low, and yellow people between the two, the lack of comprehensive census data, about 0.5 ~ 1 per thousand. 80% ~ 90% of girls with disease, China’s statistics male: female 1: 4.75. Unilateral more than bilateral, unilateral in the left side more than the right side. Area and race its incidence rate has a great difference, which is closely related to genetic factors, habits and environment, such as the habit of line double lower limbs tied swaddling babies in the area of the obvious increase in the incidence of infants born in the winter is high, may be with the low temperature of infants are mostly packaged package related. In addition, the incidence of the disease is related to the fetal position, and some statistics show that the incidence of breech birth is the highest, which is about 10 times higher than that of cephalic birth. The etiology of the disease has not yet been clarified, many factors can lead to this disease, the main factors related to this disease are as follows: 1, anatomical factors As early as 1912, Le Damary proposed the acetabular depth of the birth of the shallowest, and after that, many scholars at home and abroad through the fetal anatomical observation confirmed that the acetabular depth of the birth of a shallow, unstable hip joints; in addition, the round ligament grows fast also become the anatomical factors of the onset of the disease. 2.Genetic factors There is obvious family history of this disease, the incidence of the disease in the family can be as high as 20~30%, more obvious in sisters, which is the role of polygenic genetic factors in the development of this disease. 3, ligament laxity factors During the production process, the mother secretes a lot of estrogen, and the hip joint is in a state of laxity, if it is subjected to external force, such as breech birth, it is easy to produce dislocation. 4.Position and mechanical factors Among the cases of hip dislocation, 16%~30% are breech births, while only 3% of the normal population are breech births. Therefore, girls, preterm labor, breech birth, family history and babies with neuromuscular disorders should be highly alerted. Clinical manifestations: For newborns and infants with developmental hip dislocation, the clinical manifestations are mild and the symptoms are often not obvious. The main feature is acetabular dysplasia, living joint instability. Often can not attract the attention of parents. If the following signs are found, they should be regarded as the possibility of hip dislocation. 1, both sides of the inner thigh skin folds asymmetry, the affected side of the skin folds deepening increased. Widening of the perineum, which is more obvious in bilateral dislocation. 3, The patient’s hip joint activity is less and limited in activity. The pedal power is weaker than the healthy side. It is often in a flexed position and cannot be straightened. 4, The patient’s limbs are shortened. 5, when pulling the patient’s lower limbs, there is a popping sound or popping sensation, and sometimes the patient will cry. 6, When the lower limb is straightened or flexed, the hip joint can not be fully abducted. These phenomena are more obvious when one side of the hip is dislocated, while both sides of the hip are dislocated, the performance may not be so obvious. This is also a phenomenon that should be noted. Treatment: The pelvis develops fastest in the first year of life, especially in the neonatal period. The principle of treatment is that the earlier the better. Although the diagnosis is difficult in the neonatal period, once diagnosed, treatment is easy and will give the desired results. This is because the pathologic changes are mildest in the neonatal period and can be easily corrected. Most cases can be treated conservatively before the age of half a year with good results.