Congenital hip dislocation is more common in girls, with an incidence ratio of 6:1 in boys, due to congenital dysplasia of the acetabulum and femoral head. Once the child starts to stand or bear weight, the hip joint becomes semi-dislocated or dislocated. With the prolongation of the disease, the dislocation gradually worsens. I. Clinical manifestations 1. Before the child can stand, it is found that the perineum widens and the skin wrinkles on the hip and inner thigh increase. The hip joint on the affected side is often in a flexed position, and when the leg is straightened, it is flexed again when it is released. The affected hip also has a popping sensation when the lower limb on the affected side is pulled. For normal newborns or infants aged 2-9 months, after the two hips and two knees are flexed to 90 degrees each, the two hips can be abducted 70-80 degrees, if this angle is not reached, it should be suspected that the hip joint on that side is stunted or abnormal. 2, when the child can stand and walk, the side with hip dislocation has a limp gait, and if both sides are dislocated, it is a duck gait. The child’s waist is obviously convex when standing. Key points for diagnosis 1. If the abduction and external rotation of the affected side of the hip joint is restricted, or if the two sides of the hip and knee are flexed 90 degrees and then brought together, it can be found that the knee of the dislocated side is lower than that of the healthy side. 2. There is a popping sensation in the activity of the affected hip joint. 3.X-ray film shows that the affected side of the hip joint is subluxed or dislocation sign. Treatment principle 1. The earlier the child is treated, the better the effect. within 1 year old, the hip joint can be fixed in the reset position by frog cast, and the cast can be changed regularly until the reset is stable and no longer dislocated. 2.Children aged 1-3 years old have difficulty in resetting and often need to traction or cut off the contracted tendon of femoral adductor muscle before external fixation of frog cast. 3.It is difficult to reset the acetabulum with manual treatment for children over 4 years old, so surgical incision and reshaping of the acetabulum is needed.