Hip Dysplasia (DDH) in Babies: Leg-Length & Thigh-Fold Signs and Early Detection

When one of your baby's legs won't spread as easily during a diaper change, or the thigh folds look oddly mismatched, it's natural to wonder if something is wrong with the hip. Developmental dysplasia of the hip (DDH) is a condition where the ball of the thigh bone doesn't sit properly in the hip socket, affecting a few babies per 1,000. The good news is that how early you catch it decides everything. Found within the first weeks or months, most cases resolve with a simple brace and no surgery—but discovered after your baby starts walking, it may require surgery. That's exactly why knowing the risk factors and the signs to watch for matters so much.

⚠️ These babies should have a screening ultrasound even without symptoms: (1) born breech, (2) female, and (3) a family history of hip dysplasia in a parent or sibling. A breech girl carries the highest risk, so a hip ultrasound around 6 weeks of age is recommended.

What Is Developmental Dysplasia of the Hip?

The hip is a ball-and-socket joint where the rounded head of the thigh bone fits snugly into the cup-shaped socket of the pelvis. Developmental dysplasia of the hip happens when that fit is loose or, in severe cases, the ball slips completely out of the socket (dislocation). It used to be called "congenital hip dislocation," but because a baby whose hips are normal at birth can still worsen with growth, the term "developmental" is now preferred.

The tricky part is that it doesn't hurt. A dislocated hip causes no pain and few outward signs, so parents easily miss it. Left untreated, it can lead to unequal leg length, a limp, and early wear-and-tear arthritis later in life. That's why "let's check early" beats "let's wait and see."

Which Babies Are at Higher Risk?

DDH clusters around specific conditions. If any of the risk factors below apply, your baby should be screened even without symptoms.

• Breech position: the single strongest risk factor. Singleton babies who were breech in late pregnancy have a hip dysplasia rate of about 12.5%.
• Female sex: roughly 4-5 times more common than in boys, thought to be from greater sensitivity to the mother's relaxin hormone.
• Family history: risk rises if a parent or sibling had DDH.
• Firstborn: a first-time mother's tighter uterus can compress the baby more.
• Oligohydramnios: low amniotic fluid means less room, holding the legs in a cramped position.
• Left hip: due to typical fetal positioning, the left side is more often affected.

💡 DDH can occur with no risk factors at all, and plenty of babies with several risk factors are perfectly normal. Risk factors are a reason to screen more carefully—not a diagnosis.

Four Signs to Check at Home

Since your baby can't tell you what's wrong, your observation is the first step toward early detection. During bath time or diaper changes, look for these four things.

1. Leg-length difference

• Lay your baby down, bend the knees up with feet flat and side by side. If one knee sits lower than the other (the Galeazzi sign), the affected leg looks shorter.

2. Asymmetric thigh or buttock folds

• If the number or height of the skin folds on the inner thighs or buttocks differs noticeably between sides, it can be a clue. On its own this sign is unreliable, so weigh it alongside the others.

3. Limited hip spread

• If one leg won't spread outward and feels stiff or stuck during a diaper change, that's an important sign. Abduction that becomes increasingly limited over the first few months especially warrants a check.

4. Click or clunk

• You may feel or hear a "click" or a catch when moving the leg. A soft click is often normal, but a deep, thudding "clunk" can mean the ball is slipping in and out of the socket.

💡 After walking begins, later signs appear: a limp, toe-walking, or a waddling, duck-like gait (when both hips are involved). Treatment at this stage is more complex, so it's far better to catch it earlier.

Screening and Diagnosis

Home observation is only about finding a reason to see the doctor. Diagnosis is confirmed by exam and imaging.

Physical exam (Ortolani and Barlow tests)

• A pediatrician or orthopedist gently spreads and presses the legs to feel whether the ball slips out or back into the socket. This is routine at newborn and well-baby checks.

Ultrasound

• Before about 4-6 months, the bones are still cartilage and don't show well on X-ray, so an ultrasound is used. The American Academy of Pediatrics (AAP) recommends a hip ultrasound around 6 weeks for babies with risk factors.

X-ray

• After 4 months, the ball has hardened enough for an X-ray to assess the pelvis and joint position.

If an exam raises concern or risk factors are present, your pediatrician will refer your baby to an orthopedist for ultrasound or X-ray.

Treatment: Early Detection Is Everything

The guiding principle of DDH care is to catch it early and hold the loose joint reduced in place so the socket can develop normally. The method depends on when it's found.

Before 6 months — the Pavlik harness

• The classic treatment is the Pavlik harness, a soft strap brace that holds the legs in an M-shape (hips bent, knees spread). This position seats the ball naturally in the socket and lets the socket grow properly.
• It's usually worn for 3-6 months, and when caught early it successfully reduces the hip in about 70-80% of cases. With early diagnosis and a properly fitted harness, the risk of complications like avascular necrosis of the femoral head stays low.
• However, forcing the legs apart or fitting the harness incorrectly can cause complications, so wear it exactly as your orthopedist directs and return for regular checks.

After 6 months or if the harness fails

• If the harness doesn't reduce the hip or the problem is found later, a closed reduction under anesthesia with a hip spica cast may be needed.

Found after age one

• By then the joint has stiffened and a harness usually won't work, so traction or surgery may be required. This is exactly why early detection is stressed so heavily.

Prevention: Swaddling and Baby-Carrier Leg Position

You can't prevent DDH entirely, but simply avoiding harmful leg positions can meaningfully lower the risk. The key is not forcing the legs straight and pressed together.

Hip-healthy swaddling

• It's fine to wrap the arms, but the legs need room to bend and spread at the hips. Swaddling with the legs straightened and tightly bound makes it easier for the ball to slip out of the socket.
• In a famous example from Kyoto, Japan, a public education campaign to change tight leg-swaddling customs cut DDH incidence from 52.9 to 5.6 per 1,000 babies.

The M-position in carriers

• When carrying your baby, the ideal is an M-position where the thighs spread wider than the bottom and the knees sit slightly higher than the hips. This holds the hips in a healthy position much like a Pavlik harness does.
• Avoid narrow carriers that let the legs dangle straight down, and choose ones that support the thighs all the way to the knee.

Support Hip Health with BebeSnap

With DDH, early detection and consistent follow-up are nearly the whole battle. BebeSnap helps you track your baby's development and screening schedule so nothing slips through.

• Health records: log well-baby checkup and ultrasound dates and results so you never miss a hip-screening window.
• AI analysis: review your baby's condition through photos and records, and get help deciding when a worrying sign warrants a visit.
• Development tracking: record milestones like hip spread and first steps to compare with peers and catch red flags early.

Curious about walking milestones? See our Baby Walking Development Guide too.

Frequently Asked Questions (FAQ)

Q: Which babies must be screened for hip dysplasia?
A: Babies born breech, girls, and those with a parent or sibling who had DDH should be screened even without symptoms. Singleton breech babies in particular have a hip dysplasia rate of about 12.5%, so the AAP recommends a hip ultrasound around 6 weeks of age. When multiple risk factors overlap, screen even more proactively.

Q: How can I check for it at home?
A: During diaper changes, watch whether one leg won't spread outward, whether one knee sits lower when the knees are bent (a leg-length difference), whether the thigh or buttock folds look clearly uneven, or whether you feel a clunk when moving the leg. If any of these recur, have your pediatrician or an orthopedist examine your baby.

Q: Is swaddling bad for the hips?
A: The problem is swaddling with the legs straightened, pressed together, and bound tightly, which makes it easier for the ball to slip out of the socket. You can wrap the arms, but leave the legs room to bend and spread at the hips. In fact, DDH incidence dropped sharply after communities changed the custom of straight-leg swaddling.

Q: When does treatment start, and does it cure DDH?
A: Found before 6 months, it's treated with a Pavlik harness worn for about 3-6 months, resolving roughly 70-80% of cases, with complication risk under 1% when treated early. Found after age one, it may need traction or surgery, so early detection is the key to a full recovery.

References

• AAP Pediatrics - Evaluation and Referral for DDH in Infants
• Children's Hospital of Philadelphia - Infant Screening for DDH
• International Hip Dysplasia Institute - Hip-Healthy Swaddling
• Merck Manual (Professional) - Developmental Dysplasia of the Hip