Developmental hip dysplasia, also known as developmental hip dislocation, is the most common hip disorder in pediatric orthopedics, with an incidence rate of about 1 per 1,000, about 6 times higher in girls than in boys, about twice as high on the left side as on the right side, and about 35% bilaterally. “DDH includes hip dislocation, subluxation and acetabular dysplasia. Etiology: Caused by multiple factors. Risk factors for the disease include: girls, first births, multiple births; those with a family history; fetal malposition, such as breech, low amniotic fluid; presence of plantar inversion of the foot or myotonic plagiocephaly; and incorrect swaddling-candle wrapping. Clinical manifestations: Depending on the age of the child, the degree of dislocation, unilateral or bilateral onset, the clinical manifestations can vary, mainly as follows: 1. Children with unilateral dislocation can have hip and thigh pattern asymmetry in the early stage, but the specificity is not strong. One side of the hip joint is internalized. The perineum becomes wider in children with bilateral dislocation. 2, children with unilateral dislocation have unequal lower limbs, and children with bilateral hip dislocation during the walking period have a limp gait and duck gait.