Duck gait or wobble gait is a common sign of congenital medullary dislocation. In unilateral dislocation, lameness appears, and in bilateral dislocation, the pelvis tilts forward when standing, the hips shrug backward, the waist bulges forward, the abdomen bulges, and sways from side to side when walking, so it is called duck gait or wobble gait, and when walking slightly fast, it is easy to fall. Clinical examination methods are as follows. 1, Ortolani test and Barlow test: applicable to congenital hip dislocation between birth and 3 months, first proposed by Ortolani in 1935 and improved by Barlow. The thigh is gradually abducted and externally rotated. If there is dislocation, the femoral head can be felt embedded in the acetabular rim and produce a slight resistance to abduction. The Barlow test is the opposite of the Ortolani test, in which the examiner causes the child’s thighs to be passively inwardly retracted and internally rotated, and pushes the thumb upward against the femoral trochanter to feel a popping motion again. 2, Allis sign (Galezzi sign): make the newborn lie flat, bend the knee 85deg ~ 90deg, both legs together, both heels aligned, if the disease, the two knees are seen to be unequal in height. This is due to the upward displacement of the femur on the affected side. 3, overlap test: make the child lie down, the affected side of the hip and knee joint flexion 90deg, the examiner holds the distal femur and knee joint with one hand, the other hand presses its groin, in lifting and pushing the affected knee, if you feel the greater trochanter followed by up and down activities, then the overlap test is positive. 4, hip and knee flexion and abduction test: so that the infant examined lying down, hip and knee flexion, the examiner holds its knee with both hands, thumb in the inner knee, the remaining four fingers in the outer knee, normal infants can generally be abducted about 80deg, if only abducted 50deg ~ 60deg, is positive, can only be abducted 40deg ~ 50deg for a strong positive.