What it isStrong evidence
In hip dysplasia the socket (acetabulum) is shallow, so it covers less of the ball. Load is spread over a smaller area of cartilage, and the labrum, the rim of cartilage round the socket, takes more of it. Over time the cartilage can fray and the labrum can tear, which can lead to early arthritis.
It is present from birth (developmental dysplasia of the hip), and mild cases can go unnoticed until late childhood, puberty or adulthood. Babies and young children are checked and treated differently, with scans and harnesses, and the NHS page on developmental dysplasia of the hip covers them. This guide is for teenagers and adults.
Sources 1, 2, 3
Who gets itEmerging evidence
In 4,151 Danish adults, 3.4% had dysplasia on X-ray: about 2% in one hip and 1.4% in both. It is more common in girls and women, firstborn babies, babies who lay bottom-down (breech) in the womb, babies who were tightly swaddled, and families with hip dysplasia or loose joints (hypermobility). In a US series of 65 hips treated with surgery, 72% of the people were female and their average age was 24.
Sources 4, 2, 1, 3, 5
How it feels, and why it's found lateEmerging evidence
In that series the pain started gradually in 97% of hips. It was felt in the groin in 72% and the outer hip in 66%, came on with activity in 88% and eased with rest in 75%, and 48% of people limped. NHS sources add clicking, snapping or popping, catching or locking, a feeling the hip might give way, pain bending the hip or turning it inwards, and sometimes pain in the knee, lower back or pelvis. Pain is often mild and occasional at first, and worse with activity or at the end of the day.
In the same series it took an average of about 5 years (61.5 months), and visits to 3.3 clinicians, before the dysplasia was diagnosed. A 2026 review by physiotherapists calls adult dysplasia frequently overlooked.
Sources 5, 2, 3, 1, 6
The X-ray, the angles, and what a scan finding meansEmerging evidence
Teenagers and adults are diagnosed with an X-ray of the hips, which shows how well the socket covers the ball. The key measurement is the lateral centre-edge angle: how far the edge of the socket reaches over the ball. Definitions differ. Under 20 degrees is often used for definite dysplasia, about 18 to 25 degrees has been called borderline, and a large surgical study graded dysplasia as mild (15 degrees or more), moderate (5 to 15) or severe (under 5).
An MRI (magnetic resonance imaging) scan shows the labrum and cartilage, and a CT (computed tomography) scan gives a 3D view of the bones, mainly to plan surgery. Labral tears show up in about half of hips that don't hurt (54% in a review of studies), so a tear on a scan is common either way. The bone shape matters when your symptoms and the examination fit it.
Sources 3, 2, 4, 7, 8, 9, 10
Will it lead to arthritis?Mixed evidence
The worrying studies: in 1995, among people with one hip replaced for dysplasia, no other hip that was still working well at 65 had an angle under 16 degrees. In 172 people aged 55 or under with one hip replaced, followed for an average of 20 years, the other hip wore fastest if it was dysplastic: once early arthritis appeared, about 1 in 3 had a replacement within 10 years and 2 in 3 within 20, against 1 in 5 and 1 in 2 for other hip shapes. Both studies looked at people who already had arthritis in one hip.
The reassuring ones: in 50 Swedish adults with dysplasia in one hip and no arthritis at the start, followed for a median of 12.5 years, arthritis developed in 19 dysplastic hips and 16 normal hips, a difference that could have been chance. Of 45 borderline hips managed without surgery, 4 (9%) showed mild worsening at 15 years. So dysplasia, especially more severe dysplasia, raises the risk of earlier arthritis, but it isn't a certainty, and mild or borderline dysplasia found in adulthood often does well.
Sources 11, 12, 13, 7
Teenagers
Most teenage dysplasia is mild dysplasia that was missed or not treated in infancy. A teenager with mild dysplasia and few symptoms may be monitored with a check every 6 to 12 months, and activity changes, physiotherapy and, if needed, an osteotomy are the options.
Sudden hip, thigh or knee pain, a limp, or not wanting to take weight is different and urgent. A slipped growth plate at the top of the thigh bone (slipped capital femoral epiphysis) is most common at 12 to 16 in boys and 10 to 14 in girls, and can be felt only in the knee or thigh. Growing pains affect both legs in the evening or at night, go by the morning, and don't cause a limp or pain in one joint.
Sources 1, 14, 15, 16
How it differs from impingement and labral tears
Hip impingement is the opposite shape problem: too much bone, which pinches when you bend deeply, while dysplasia is too little cover, so the hip may feel unstable. The two can occur together, and hips with both a bony bump on the ball (a cam) and dysplasia wore fastest in one study. Labral tears often come with dysplasia; the labral tear guide covers them. Established arthritis is covered in the hip arthritis guide, and loose joints in our guide to exercise with hypermobility.
Sources 12, 10
