What Is Hip Dysplasia in Adults? Signs and Treatment

Hip dysplasia in adults is a structural problem in which the hip socket (acetabulum) is too shallow or angled incorrectly, leaving the ball of the thigh bone without enough bony coverage. This means the joint bears weight unevenly, concentrating force on a small strip of cartilage and the rim of the socket instead of spreading it across a broad surface. Most adults with hip dysplasia were born with the condition or developed it during childhood, though it may not cause noticeable pain until the twenties, thirties, or even later. Because the hip looks normal from the outside and the pain often starts subtly, the diagnosis is frequently delayed by years.

Where Adult Hip Dysplasia Comes From

In most cases, hip dysplasia in adults traces back to the growing years. The two main origins are residual childhood developmental dysplasia of the hip (DDH) and acetabular dysplasia that appears during adolescence. These are distinct processes that affect the hip at different stages of skeletal growth, but both produce a similar shallow-socket deformity and follow a similar path toward joint breakdown.¹ Some people were screened as infants and told they were fine; others were treated with a harness as babies and assumed the problem resolved. A subset genuinely develop the shallow socket geometry during their teenage growth spurt, with no abnormality detectable in early childhood.

Genetics play a meaningful role. A large genome-wide study estimated that roughly 55% of DDH susceptibility can be attributed to common genetic variants, spread across the regular chromosomes and the X chromosome. The gene with the strongest and most consistent link is GDF5, which encodes a growth factor involved in joint and cartilage development.² Multiple candidate gene studies and functional work have reinforced that connection.³ This means hip dysplasia runs in families, and if a parent or sibling was treated for it, your own risk is higher than average.

Who Is Most Affected

Hip dysplasia shows up in both sexes, but women are affected more often. A systematic review of studies covering nearly 6,000 hips found the prevalence of radiographic hip dysplasia in the general adult population was about 3.8% in women and 2.7% in men.⁴ DDH is commonly found in women presenting to routine orthopedic clinics.⁵ There is also evidence that female sex modifies the risk of hip osteoarthritis related to acetabular dysplasia, meaning the downstream consequences may be disproportionately felt by women as well.⁶

Signs and Symptoms

The hallmark of adult hip dysplasia is pain that creeps in gradually rather than arriving with a single injury. In a study of skeletally mature patients with symptomatic acetabular dysplasia, the onset was insidious in 97% of cases, and about three-quarters reported moderate-to-severe pain on a daily basis.⁷ The most common location was the groin, reported in roughly 72% of hips, followed by the side of the hip in about 66%. Pain typically worsened with activity and improved with rest.

On physical examination, about half of the patients in that study walked with a limp, and close to 40% showed a positive Trendelenburg sign, where the pelvis drops on the opposite side during single-leg stance because the hip abductor muscles cannot stabilize effectively.⁷ Nearly all had a positive impingement sign when the hip was flexed and rotated inward. Many people describe a catching or clicking sensation, difficulty sitting for long periods, and aching after exercise. The pain pattern can overlap with groin strains, labral tears from sports, or even low back problems, which is one reason the condition is frequently misdiagnosed early on.

What Is Happening Inside the Joint

Because the socket does not wrap around the femoral head sufficiently, the contact area that shares the load is much smaller than in a normal hip. Finite element models show that a dysplastic joint generates high stresses along the acetabular rim during ordinary walking, and these high-stress zones correspond to the locations where cartilage and labral damage is observed clinically.⁸ Older patients with dysplasia tend to have sockets that have deformed further from a spherical shape, which correlates with even higher peak contact stresses before surgery.⁹

The skeletal geometry also affects the muscles around the hip. Studies using imaging and musculoskeletal modeling have found that people with dysplasia have more lateralized hip joint centers, meaning the ball sits further from the body’s midline. This shortens the lever arm that the gluteal muscles use to stabilize the pelvis, so the muscles have to work harder to do the same job. Patients with DDH show significantly reduced abductor muscle moment arms, creating a chronic biomechanical disadvantage that increases the forces driven into the joint cartilage.¹⁰ Interestingly, the same study found that these patients had larger gluteus medius muscle volumes, suggesting the muscles try to compensate by growing, though the unfavorable leverage still limits their effectiveness.

Labral Tears and Cartilage Damage

The labrum is a ring of fibrous cartilage that lines the edge of the hip socket, acting as a seal and a shock absorber. In a dysplastic hip, the labrum bears an outsized share of the load because the bony rim does not provide adequate coverage. The result is that labral tears are nearly universal in symptomatic dysplasia: one review found labral pathology in up to 90% of cases,¹¹ and a systematic review reported an average prevalence of labral tears around 79% in dysplastic hips.¹² These tears often represent the labrum being ground down over years of abnormal loading rather than a single traumatic event.

This is clinically important because a labral tear in a dysplastic hip behaves differently from one in a structurally normal hip. Arthroscopic repair of the labrum alone, without correcting the underlying socket deformity, tends to produce poor results because the forces that tore it in the first place remain unchanged. That distinction drives much of the treatment decision-making.

How the Diagnosis Is Made

Diagnosis starts with a standard pelvic X-ray. The key measurement is the lateral center-edge angle, which quantifies how much of the femoral head is covered by the bony roof of the socket. An angle below about 20 degrees is generally considered dysplastic. Clinicians also look at the Tönnis angle, the shape of the lateral sourcil (the dense line at the weight-bearing edge of the socket), and whether the labrum appears everted.¹³ A false-profile X-ray taken from an oblique angle adds information about how much the socket covers the front of the femoral head.¹⁴

If surgery is being considered, a CT scan can provide more precise measurements of both the front and back coverage of the socket, along with the twist of the femur bone (femoral anteversion).¹⁴ MRI is typically added to evaluate the labrum, cartilage surface, and any early degenerative changes. Reliability studies have shown that measurements like the center-edge angle and migration percentage can be taken in both standing and supine positions, though standing films may better reflect the joint’s behavior under load.¹⁵

The Problem of Delayed Diagnosis

One of the most frustrating aspects of adult hip dysplasia is how long it takes to get the right diagnosis. A study tracking patients from their first visit to a general practitioner to their eventual review at a specialized young adult hip clinic found a mean delay of over 40 months.¹⁶ That matters because the same study showed that patients referred later had lower hip scores, lower general health scores, and higher grades of osteoarthritis on imaging. A larger proportion of late-referred patients ended up needing a total hip replacement rather than a joint-preserving osteotomy. The implication is straightforward: early recognition opens the door to treatments that preserve the natural joint, while delays narrow those options.

Conservative Treatment

Exercise and physical therapy are typically the first line of management, though the evidence base specifically for hip dysplasia is still catching up. A recent review noted that evidence for nonsurgical management, including exercise and education, is emerging but remains limited, and clinicians should combine what research exists with clinical reasoning while considering outcomes beyond pain alone, such as quality of life and the ability to participate in daily activities.¹⁷

That said, the studies that do exist are encouraging. Hip abductor strengthening exercises improved abductor muscle strength by about 16% in one trial, and patients showed significantly better hip stability during walking and reduced pain scores afterward.¹⁸ A feasibility study of progressive resistance training in patients with hip dysplasia found high adherence, few adverse events, improved patient-reported outcomes on four of six subscales, and significant gains in hip flexion strength and functional jumping performance.¹⁹ The logic behind strengthening is that it cannot fix the bony anatomy, but it can help the muscles compensate for the mechanical disadvantage and potentially slow the rate of cartilage breakdown.

Diagnostic hip injections, where a local anesthetic and sometimes a corticosteroid are injected into the joint under imaging guidance, serve a dual purpose. They can provide temporary pain relief, and they help confirm that the hip joint itself is the source of pain. A study of injection outcomes found that if someone does not respond to a diagnostic injection, it is a strong negative predictor of surgical outcome, meaning surgery on that hip is less likely to help.²⁰

Joint-Preserving Surgery

For younger, active patients whose cartilage is still in good shape, the main surgical option is periacetabular osteotomy (PAO). The procedure involves making controlled cuts in the bone around the hip socket, then rotating the socket into a better position so it covers more of the femoral head. The Bernese PAO, the most widely used technique, preserves the weight-bearing posterior column of the pelvis, maintains the blood supply to the socket, and keeps the hip abductor muscles attached.²¹ It is generally offered to patients whose growth plates have closed (usually after age 10) up to around age 40, though the exact upper limit depends on how much arthritis has already developed.

Long-term data show that PAO can delay or prevent the need for a total hip replacement, though it does not work for everyone. An 18-year follow-up study found that about 74% of hips had not required a hip replacement. Roughly 53% of hips remained asymptomatic at last follow-up, while 26% still had significant symptoms even without progressing to replacement.²² A separate large consecutive series reported high rates of long-term patient satisfaction across pain relief, daily activities, and recreational ability.²³ These numbers mean PAO buys many patients decades of improved function, though some will eventually need a replacement regardless.

When a Hip Replacement Is the Answer

If significant arthritis has already set in or the patient is older, total hip arthroplasty (THA) becomes the more appropriate procedure. Dysplastic hips present technical challenges during replacement surgery because the socket is shallow and sometimes poorly positioned, which can make it harder to get a stable implant. In some cases, surgeons graft bone onto the acetabular roof to provide enough support for the implant cup.²⁴ Despite these added difficulties, modern hip replacement is highly effective at relieving pain and restoring function in dysplastic hips.

The progression to needing a replacement is not inevitable, but it is considerably more likely than in people with normal hip anatomy. A study tracking the natural history of osteoarthritis found that joint degeneration was most rapid in patients with DDH. Among patients who had already developed mild degenerative changes, roughly one in three with DDH needed a hip replacement within 10 years, and about two in three did within 20 years.²⁵ A review of published literature also concluded that hip dysplasia diagnosed after skeletal maturity is associated with osteoarthritis development over time in the majority of studies, though some researchers have questioned how reliably simple radiographic measurements predict who will progress.²⁶

Recovery and Returning to Sports After PAO

PAO is a substantial operation, and recovery is measured in months, not weeks. Most rehabilitation protocols begin with partial weight-bearing on crutches starting the day after surgery, continuing for roughly six to eight weeks. Hip flexion is typically limited to 90 degrees and external rotation restricted during the early weeks to protect the healing bone.²⁷ A systematic review found that return to sporting activities is generally recommended between six and twelve months postoperatively, and that delaying weight-bearing was associated with a lower incidence of pelvic fractures compared to immediate full weight-bearing.²⁸

The return-to-sport numbers are encouraging. A study of patients with borderline hip dysplasia found that about 93% of preoperatively active patients returned to sports, with most resuming activity by six months. Activity scores improved significantly, and patients were able to increase both how often and how long they exercised.²⁹ A study of adolescent and young adult athletes found that 80% returned to play at a median of nine months, with about 73% getting back to the same level. Recreational athletes fared better than competitive athletes in reaching their pre-injury level.³⁰ A well-structured rehabilitation program plays a key role: one study showed that heavy daily activities and recreational sports were improved after completing a comprehensive post-operative rehab program.³¹

Living With Hip Dysplasia Beyond the Physical

The impact of hip dysplasia on young adults goes beyond joint mechanics. Qualitative research has captured how persistent pain affects self-image, social engagement, and mental health. Participants in one study described becoming isolated because everyday tasks like walking to a coffee shop became painful, and that isolation eroded their confidence and willingness to go out.³² Another qualitative study found that living with DDH challenged patients’ perception of themselves as young, active, and independent. Pain took on a life of its own, influencing not just what patients could do but how they saw themselves.³³ The condition is often invisible to others, which can make it harder to get understanding from employers, friends, or even family members who see a young person without an obvious disability.

Pregnancy After Periacetabular Osteotomy

Because hip dysplasia disproportionately affects women, and PAO is often performed during the reproductive years, pregnancy and childbirth come up frequently. The concern is that the bony cuts and repositioning might alter the pelvic dimensions enough to affect delivery. In practice, the data are somewhat mixed. One study found that 53% of deliveries after PAO were by cesarean section, which was significantly higher than the national average of about 32%.³⁴ However, only one patient in that study suffered a pregnancy-related complication, and the rates of preterm delivery and low-birth-weight infants were not significantly different from national data.

A separate study reported a similar cesarean rate of about 55%, but noted that the majority of those cesarean deliveries were performed for standard obstetric reasons like breech presentation or failure to progress, not specifically because of the PAO. Only about 27% of the cesarean patients said the surgery was performed because of their osteotomy history.³⁵ About half of the patients said their obstetrician had expressed some concern about the PAO affecting delivery, which suggests the elevated cesarean rate is partly driven by caution from providers who are unfamiliar with the procedure. Vaginal delivery is not ruled out after PAO, but having a conversation early in pregnancy with both the obstetrician and the orthopedic surgeon who performed the osteotomy is a sensible step.