What Exactly Does Hip Dysplasia Mean for Babies?

Hips support your body weight while standing, walking, squatting, and climbing stairs. This important joint consists of a "ball" (the top of your thigh bone) fitting into a "socket" (your pelvis). The ball easily rotates within the socket to perform daily tasks—unless you're born with a relatively common condition called hip dysplasia, also known as developmental dysplasia of the hip (DDH).

"Hip dysplasia is basically a spectrum of problems relating to how the hip develops," says Dr. Scott Rosenfeld, M.D., FAAP, an orthopedic surgeon and director of the Hip Preservation Program at Texas Children's Hospital. "It usually happens when the socket is too shallow for the ball, which results in instability of the hips." In other words, the ball doesn't fit inside of the socket, causing the joint to mold improperly as Baby's soft cartilage hardens into bone. The condition ranges from mild (loose joints) to severe (complete dislocation), but it doesn't cause any pain.

Hip dysplasia is the most common musculoskeletal or bone and joint abnormality in babies, says Dr. Rosenfeld. In fact, one in every 100 babies are treated for hip dysplasia, while one in 500 babies have completely dislocated hips at birth, according to the International Hip Dysplasia Institute. Diagnosis and treatment usually happens early, preventing any health problems down the road. Here's everything you need to know about the causes, symptoms, and treatment options for hip dysplasia in babies.

What Causes Hip Dysplasia?

According to Dr. Rosenfeld, hip dysplasia doesn't have known causes in most babies. However, it's associated with five major risk factors:

A family history of hip dysplasia. According to the International Hip Dysplasia Institute, children with a family history of the condition are 12 times more likely to develop it.

Breech presentation. A baby is breech when the buttocks or feet are near the mother's cervix, meaning they'll come first during delivery.

Being the first-born child. This circumstance increases the probability of hip dysplasia because a mother's womb is tighter during her first pregnancy, thus restricting fetal movement, says Dr. Rosenfeld. The International Hip Dysplasia Institute says that 6 out of 10 cases of hip dysplasia occur in first-born children.

Being female. Doctors speculate that female babies are more responsive to pregnancy hormones called relaxin, which loosen ligaments and relax muscles. About 80% of hip dysplasia patients are female.

Oligohydamnios. Dr. Rosenfeld says that babies with oligohydamnios—or low amniotic fluid levels— also have restricted movement in the womb.

Out of these five factors, the most important are family history and breech presentation. Dr. Rosenfeld says that if he sees a baby with both circumstances, he automatically assumes they have hip dysplasia "unless we prove otherwise with testing." Hip dysplasia is also more common in the left hip, according to Ernest L. Sink, M.D., co-director of the Hospital for Special Surgery's Center for Hip Preservation.

Babies can also get developmental dysplasia of the hip after birth, especially if their legs are kept straight during swaddling. This forced position loosens the joints of the hips and manipulates the soft cartilage, says the International Hip Dysplasia Institute. Parents should always research best practices before swaddling their baby.

How is Hip Dysplasia Diagnosed?

Doctors test every newborn for hip instability with a variety of maneuvers. "With hip dysplasia, they can feel the hip joint 'clunk' and pop in and out of the socket," says Dr. Sink. Physical exams aren't 100% effective, though, and results largely depends on whether the baby is relaxed. What's more, pediatricians might not detect shallow hip sockets that aren't dislocated. That's why babies with apparent risk factors—like family history and breech presentation—often need additional testing with an ultrasound.

Signs of Hip Dysplasia

If hip dysplasia is missed during the pediatric exam, it can be harder to diagnose later in life. The condition isn't painful and doesn't have obvious symptoms. However, parents might notice that one of their child's legs appear longer than the other, says Dr. Sink. If both hips are dislocated, the child may waddle—but Dr. Rosenfeld notes that most toddlers walk funny, so it can be hard to pinpoint this discrepancy. Other symptoms include hip clicking, asymmetrical buttock creases, and inflexibility of the hips.

Hip Dysplasia Treatment

Untreated hip dysplasia doesn't always lead to complications. However, since the hip isn't growing properly, children might suffer from a limp or uneven leg lengths. Adolescents might experience discomfort, while adults could develop hip labral tears or osteoarthritis. "It's actually the most common cause of early-onset hip arthritis in young women," says Dr. Rosenfeld.

Hip dysplasia treatment depends on the baby's age and the severity of symptoms.

Pavlik Harness

"If the hip is unstable—coming in and out of the joint—the routine treatment is a Pavlik harness," says Dr. Sink. Pavilk harnesses resemble soft suspenders. They mold the ball into the socket of the hip—which is especially important as your baby's soft cartilage develops into bone. Pavlik harnesses are the go-to treatment option until Baby is four to six weeks old.

Babies usually wear a Pavlik harness for six weeks, then doctors examine results with an ultrasound. If everything looks normal, the baby begins weaning off it for several more weeks. If the hips still appear dislocated, the harness will be worn longer—and occasionally the baby will need surgery. Dr. Sink says that Pavlik harnesses are anywhere from 60%-90% effective in treating hip dysplasia.

Closed Reduction

For children between six weeks and one year old, hip dysplasia is usually treated with a minimally-invasive closed reduction procedure. Your baby will be put under anesthesia, and the doctor will position the hip correctly in the socket, says Dr. Sink. He adds that Baby will wear a spica cast for a few months to hold everything in place. Follow-up tests and MRIs will confirm the surgery's success.

Open Reduction

Anyone older than 12 months will need open reduction surgery. It's also completed if close reduction wasn't successful or if the hip dysplasia is severe. When the child is under general anesthetic, the doctor will make an incision to reposition the hip socket and repair the ligaments. After surgery, the child will need to wear a spica cast to immobilize the hip.