In a normal hip joint, the rounded top of the thigh bone (femur) fits into a cup-shaped socket in the pelvis called the acetabulum. This type of joint is called a ball-and-socket joint.
In developmental dysplasia of the hip, the top of the femur moves in and out of the socket either part way or all the way. When it moves all the way out of the socket, it is called a dislocation. This happens when the ligaments that hold the two bones together are very loose or because the cup-shaped socket is not deep enough.
This condition usually is present at birth. But it can develop during infancy or childhood.
If the bones in the joint are not in the right place, the hip and femur can't grow normally. This can lead to:
A shortened leg