Developmental dysplasia of the hip (DDH) is a dislocation of the hip joint that is present at birth. The condition is found in babies or young children.

The hip is a ball and socket joint. The ball, called the femoral head, forms the top part of the thigh bone (femur) and the socket (acetabulum) forms in the pelvis.

The hip may be all the way out of the joint or the socket may be a little shallow. One or both hips may be involved.

The cause is unknown, but genetic factors may play a role. Low levels of amniotic fluid in the womb during pregnancy can increase a baby's risk of DDH. Other risk factors include:

• Being the first child
• Being female
• Breech delivery
• Family history of the disorder

DDH occurs in about 1 out of 1,000 births.

There may be no symptoms. Symptoms that may occur can include:

• Different (asymmetric) leg positions
• Reduced movement on the side of the body affected by the dislocation
• Shorter leg on the affected side
• Uneven folds of thigh fat

After 3 months of age, the affected leg may turn outward or be shorter than the other leg

Pediatricians routinely screen all newborns and infants for hip dysplasia. There are several methods to detect a dislocated hip or a hip that is able to be dislocated.

Ultrasound of the hip is the most important method to show the hip problem. An x-ray of the hip joint may help diagnose the condition in older infants and children.

A hip that is truly dislocated in an infant should be detected at birth, but some cases are mild and symptoms may not develop until after birth, which is why multiple exams are recommended. Some mild cases are silent and cannot be found during a physical exam.