Duck or wobbling gait is a common sign of congenital medullary dislocation. In unilateral dislocation, limp appears, and in bilateral dislocation, the pelvis tilts forward when standing, the hips are shrugged back, the waist is convex, and the abdomen is bulged, so it is called duck or wobbling gait when walking from side to side, and it is easy to fall when walking slightly fast. Clinical diagnosis can be made according to the performance. 1, neonatal and infant manifestations: 1, joint movement disorders: the affected limb is often flexed, poor activity than the healthy side, pedaling power is located on the other side. The hip joint abduction is limited. 2.Shortening of the affected limb: the affected femoral head is dislocated posteriorly and superiorly, and the corresponding shortening of the lower limb is common. 3.Changes in skin lines and perineum: asymmetric skin folds on the buttocks and inner thighs, deeper skin lines on the affected side than on the healthy side and increased in number. Infant girls have asymmetrical labia majora and widened perineum. Second, the manifestations of early childhood: 1, limping gait: limping is often the only complaint of parents when the pediatrician visits the clinic. When one side is dislocated, it is manifested as lameness; when bilateral dislocation is manifested as duck gait, the child’s hip is obviously posteriorly protruding, and the waist foreshortening is increasing. 2.Shortening deformity of the affected limb: In addition to shortening, there is also inversion deformity.