Hip Dysplasia (DDH)

What hip dysplasia is

The hip is a ball-and-socket joint. In a healthy hip the socket covers most of the femoral head like a cup. In dysplasia the cup is too shallow or tilted, so:

• the ball can slide partly out (subluxation) or fully out (dislocation), mostly in babies
• in adults, body weight is carried on a small rim of cartilage, which overloads the edge of the socket and the labrum (a ring of cartilage around it)

A baby's hip is formed of soft cartilage that shapes itself around a well-seated ball. If the ball is not centered in the first months, the socket does not deepen normally. That is why early detection works so well.

Risk factors

• Breech position in the last weeks of pregnancy, the strongest risk factor
• Female sex: girls are affected several times more often than boys
• Family history in a parent or sibling
• First pregnancy and low amniotic fluid, which limit space in the womb
• Tight swaddling with the legs held straight and together
• Other "packaging" conditions such as torticollis and foot deformities
• In adults: joint hypermobility and some connective tissue disorders

The left hip is affected most often.

Hip dysplasia in babies

Signs

Many babies have no visible signs, so routine examination matters. Possible clues:

• a clunk when the hip is moved during an exam or diaper change
• legs of different lengths, or knees at different heights when the baby lies with hips and knees bent
• uneven skin folds on the thighs or buttocks (common in healthy babies too, so not a reliable sign alone)
• one leg that does not open out (abduct) as far as the other
• later, a waddling gait, walking on tiptoe on one side, or limping

Hip dysplasia in babies is not painful.

Screening and diagnosis

• Newborn exam: the Ortolani and Barlow maneuvers gently test whether the hip can be pushed out or clunked back in. They are most useful in the first 2 to 3 months.
• Ultrasound: the best test before 4 to 6 months, when the hip is still mostly cartilage. Usually done at about 6 weeks for babies with risk factors, because many loose newborn hips tighten on their own in the first weeks.
• X-ray: used after about 4 to 6 months, once bone has formed in the femoral head.

Treatment in babies

Regular ultrasounds or X-rays follow treatment until the hip has developed normally, often until the child has finished growing.

Hip dysplasia in teens and adults

Milder dysplasia often goes undiagnosed until the cartilage starts to wear. It is a leading cause of hip arthritis in women under 50.

Symptoms

• deep groin pain, sometimes felt at the side of the hip or the buttock
• pain with walking, running, prolonged standing or sitting
• catching, locking or clicking, often from a labral tear
• a limp or tired feeling around the hip at the end of the day
• reduced range of motion as arthritis develops

Diagnosis

A standing pelvis X-ray measures the lateral center-edge angle, which shows how much the socket covers the ball. An angle under about 20 degrees indicates dysplasia, and 20 to 25 degrees is borderline. CT shows the socket's 3D shape, and MRI (often with contrast) shows the labrum and cartilage.

Treatment

• Non-surgical care: physical therapy to strengthen the hip and core muscles, activity changes, weight management and anti-inflammatory pain relief at the label dose. This helps symptoms but does not change the socket shape.
• Periacetabular osteotomy (PAO): the socket is cut free and rotated to cover the ball properly. It is best for younger adults with little arthritis and can delay or prevent hip replacement for many years.
• Hip arthroscopy: keyhole repair of a labral tear, usually combined with a PAO in true dysplasia, since arthroscopy alone can worsen instability.
• Total hip replacement: when significant osteoarthritis has developed.

Outlook

Babies treated early usually develop normal hips and have no long-term problems. Late diagnosis needs more complex treatment, and residual dysplasia raises the risk of arthritis in early adulthood. In adults, hip preservation surgery done before major cartilage loss gives the best long-term results.

Prevention

You cannot prevent most dysplasia, but you can avoid making it worse. Use hip-healthy swaddling that leaves room for the legs to bend up and out, and choose baby carriers and car seats that support the thighs in a spread "M" position. Keep up with well-baby hip checks, and ask about an ultrasound if your baby was breech or there is a family history.

Frequently asked questions

What are the signs of hip dysplasia in babies?

Possible signs include a clunk when the hip moves, uneven leg lengths, uneven thigh creases, and one leg that does not spread outward as far. Many babies show no signs, which is why doctors check the hips at newborn and early well-baby visits and use ultrasound for babies at risk.

Can hip dysplasia correct itself?

Mild looseness in newborn hips often settles by itself in the first 6 weeks, which is why ultrasound is usually done after that. True dysplasia that persists needs treatment, because the socket will not deepen normally unless the ball is held in place.

What are the symptoms of hip dysplasia in adults?

The typical symptom is deep groin or hip pain that comes on with activity and builds over months or years, often with clicking, catching or a limp. It mostly affects young and middle-aged women and can lead to a labral tear or early arthritis.

How long does a baby wear a Pavlik harness?

Usually full-time for about 6 to 12 weeks, sometimes followed by part-time wear, with regular ultrasound checks. The harness is adjusted by the orthopedic team. Babies can feed and sleep normally in it, and most adapt within a few days.

Is hip dysplasia genetic?

It runs in families. A baby with a parent or sibling who had hip dysplasia has a higher risk, so they are usually offered a screening ultrasound even if the exam is normal. Many cases occur without any family history.