The hip is a ball and socket joint with the ball (called the femoral head) coming from the top part of the femur (thigh bone) and the socket (called the acetabulum) coming from the pelvis. Developmental hip dislocation varies in the degree of malformation. The hip may be all the way out of the joint or the acetabulum may simply be a little shallow.

The cause is unknown, but genetic factors may play a role. Problems resulting from very mild developmental dysplasia of the hip may not become apparent until the person is in their 30's or 40's.

One or both hips may be involved. Risk factors include being the first child, being female, a breech delivery, and a family history of the disorder. It occurs in about 1 out of 1,000 births.

• Diminished movement in the affected side
• Asymmetry in leg positions
• Asymmetry of the thigh fat folds
• After 3 months of age, asymmetry of rotation of the leg and apparent shortening of the affected leg

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

A hip that is truly dislocated in an infant should be picked up, but some cases are subtle and some develop after birth, which is why multiple examinations are recommended. Some mild cases are "silent" and cannot be picked up on physical exam.

Ultrasound of the hip is the most important imaging study and will demonstrate hip deformity. A hip X-ray (joint X-ray) is helpful in older infants and children.

In early infancy, positioning with a device to keep the legs apart and turned outward (frog-leg position) will usually hold the femoral head in the socket. If there is difficulty in maintaining proper position, a cast may be applied and changed periodically to accommodate growth.

Surgery may be necessary if early measures to reduce the joint (put the joint back in place) are unsuccessful, or if the defect is first detected in an older child.

If the dysplasia is picked up in the first few months of life, it can almost always be treated successfully with bracing. In a few cases, surgery is necessary to put the hip back in joint. An older age at diagnosis may be associated with a worse outcome and may necessitate more complex surgery to repair the problem.

• Skin irritation from reduction devices
• Untreated, will lead to arthritis and deterioration of the hip which can be severely debilitating
• Limb length discrepancies may persist despite appropriate treatment

Call your health care provider if you suspect that your child's hip is not properly positioned.

Prevention is probably not possible, but early detection and treatment before complications occur is of paramount importance.