Pelvic dysplasia, more precisely called developmental dysplasia of the hip (DDH), is a condition in which the hip socket does not fully cover the ball of the thighbone, leaving the joint unstable and prone to damage over time. It ranges from a mildly shallow socket to a hip that has completely slipped out of place. The condition can be caught at birth, show up in childhood, or go unrecognized until adulthood, when pain and stiffness finally drive someone to get imaging. What you can expect depends heavily on when the problem is identified and how severe it is, but the overall trajectory of the condition is well understood.
What Is Actually Happening in the Joint
A normal hip socket, called the acetabulum, wraps around the head of the femur like a deep cup, distributing the forces of walking and standing across a broad area of cartilage. In a dysplastic hip, that cup is too shallow, too steep, or angled in a way that leaves part of the femoral head exposed. The result is that weight-bearing forces get concentrated onto a smaller patch of cartilage instead of being spread evenly.1PubMed Central. Morphology of the dysplastic hip and the relationship with sex and acetabular version Studies using computer modeling have confirmed that cartilage contact area is generally smaller in dysplastic hips, and the pressure on the remaining contact zone goes up.2PubMed. Finite element analysis of mechanical behavior of human dysplastic hip joints: a systematic review Over years, that chronic overload wears down cartilage and raises the risk of early-onset arthritis.3PubMed Central. Cartilage contact pressure elevations in dysplastic hips: a chronic overload model
The undercoverage can occur along several axes. Some hips are primarily deficient on top, where most of the load falls during walking. Others lack coverage toward the front of the socket, which matters during activities like climbing stairs or deep squatting. Some have deficiencies in multiple directions at once.4Journal of Hip Preservation Surgery. FP6.2 Anatomy in borderline hip dysplasia, beyond the center edge angle. A CT comparative study This variability is one reason dysplasia can present so differently from person to person.
What Causes It
DDH is not caused by a single thing. It sits at the intersection of genetics and physical environment, with several well-established risk factors stacking on top of one another.
A meta-analysis of cohort studies found that being female carried the largest independent risk, with girls roughly seven times more likely to develop DDH than boys. Breech position at delivery was associated with about a fourfold increase, and having a family history of the condition carried a similar risk. Other factors included being a firstborn, having low amniotic fluid during pregnancy, being delivered by cesarean section, and the presence of other musculoskeletal issues at birth.5PubMed. Risk factors of developmental dysplasia of the hip in infants: A meta-analysis based on cohort studies
The breech connection is thought to be mechanical. Toward the end of pregnancy, a baby in breech position experiences sustained pressure on the hip joints from the mother’s pelvis and from the baby’s own extended legs pressing against the socket. The longer a fetus stays in breech, the higher the risk.6PubMed Central. Association between timing and duration of breech presentation during pregnancy and developmental dysplasia of the hip: A case-control study Biomechanical modeling has shown that fetal kick forces and the resulting stress on cartilage are significantly lower in breech position and when amniotic fluid is low, suggesting that the developing hip needs normal movement to form properly.7PubMed Central. Altered biomechanical stimulation of the developing hip joint in presence of hip dysplasia risk factors
The Genetic Side
Family history is one of the strongest predictors, and it is already used as a screening criterion in most programs.8PubMed Central. Genetics of hip dysplasia – a systematic literature review The genetics, though, are not simple. No single gene causes DDH. Instead, numerous genes appear to contribute, each adding a small amount of susceptibility. These genes likely influence things like connective tissue laxity and the pace of bone and cartilage development. The mix of genetic predisposition and environmental triggers helps explain why DDH rates vary so much between populations.9PubMed Central. Current knowledge on the genetic background of developmental dysplasia of the hip and the histomorphological status of the cartilage
Signs in Newborns and Infants
In newborns, the classic screening tests are the Ortolani and Barlow maneuvers, performed during routine physical exams. The Ortolani test checks whether a dislocated hip can be guided back into the socket; the Barlow test checks whether a hip in the socket can be pushed back out.10PubMed Central. Developmental dysplasia of the hip Both rely heavily on the examiner’s experience and the amount of manual pressure applied, which means results can vary between clinicians.11PubMed Central. Instability Testing for Congenital Hip Dislocation: Knee Extension Provokes Hip Dislocation
A study of referred infants found that the Ortolani test had a positive predictive value between roughly 40% and 60%, meaning a positive result is a strong signal but not a guarantee of a problem. The Barlow test was far less reliable on its own, with a positive predictive value below 16%.12PubMed. The Ortolani test has a high positive predictive value in clinical hip screening for developmental dysplasia of the hip Beyond these specific maneuvers, parents and clinicians may notice uneven skin folds around the thighs, a leg that appears shorter on one side, or limited ability to spread the hips apart during diaper changes. Any of these signs usually triggers an ultrasound.
How Infants Are Imaged
Because a newborn’s hip is mostly cartilage and does not show up well on X-ray, ultrasound is the go-to imaging tool. The Graf method, developed in 1980, measures two angles that describe how much of the femoral head is covered by the bony roof and the cartilage rim of the socket. Hips are then classified into types ranging from normal (type I) to fully dislocated (type IV), and the classification directly guides whether treatment is needed.13PubMed. Ultrasonographic screening for developmental dysplasia of the hip: the Graf method revisited In many European countries, the Graf method is considered the gold standard for infant hip screening.
A large single-institution screening study found that about 92.5% of newborn hips were fully mature at first exam, around 7% were still maturing but not yet abnormal, and only about 0.3% were classified as pathological.14PubMed. Early neonatal universal ultrasound screening for developmental dysplasia of the hip: a single institution observational study That low pathological rate is reassuring but also highlights why some countries debate whether every newborn should be screened with ultrasound or only those with known risk factors. Comparisons between universal and selective screening approaches have shown a trend toward fewer late-detected cases when every infant is scanned, though the differences in studies so far have not been large enough to reach statistical significance.15PubMed Central. Universal or selective ultrasound screening for developmental dysplasia of the hip? A discussion of the key issues
Signs in Adults
Many people with mild dysplasia never know they have it until their twenties, thirties, or later, when the joint starts to protest. The most common complaint is groin pain, reported by about 72% of adults with symptomatic acetabular dysplasia. Pain along the outer side of the hip is nearly as common, affecting about 66% of patients. The pain tends to be activity-related, and most people find that cutting back on physical activity helps, at least temporarily.16Journal of Bone and Joint Surgery. Clinical Presentation of Symptomatic Acetabular Dysplasia in Skeletally Mature Patients
People often describe a catching or clicking sensation, especially during movements that load the hip in its weakest direction. Sitting for long periods, running, or walking on uneven ground can aggravate things. Because the hip compensates by shifting loads to surrounding structures, some adults with undiagnosed dysplasia present initially with what looks like lower-back pain, knee pain, or groin muscle strains rather than classic hip symptoms.
The Labrum Problem
The labrum is a ring of cartilage lining the rim of the hip socket, acting like a gasket that deepens the cup and helps seal in joint fluid. In a dysplastic hip, the labrum has to do an outsized job because the bony socket is not contributing its share of coverage. Over time, this overwork damages the labrum. In symptomatic dysplastic hips, labral tears are found in up to 90% of cases.17PubMed Central. The role of the acetabular labrum in hip dysplasia. A literature overview.
The pattern of these tears differs from what you see in other hip conditions. In hips with femoroacetabular impingement, tears tend to cluster at the front of the socket because the ball is jamming into the rim. In dysplastic hips, tears can appear more broadly and involve different modes of damage, reflecting the way the femoral head is slipping rather than jamming.18PubMed. Differences in the locations and modes of labral tearing between dysplastic hips and those with femoroacetabular impingement This distinction matters because repairing a labral tear in a dysplastic hip without also fixing the underlying bony problem is unlikely to provide lasting relief.
Diagnosing Adults
In adults, X-rays replace ultrasound as the primary imaging tool. Clinicians use a set of measurements taken from standard pelvic and hip radiographs. The lateral center-edge angle is the most widely used: it measures how far the bony roof of the socket extends over the femoral head. An angle below about 20 degrees is generally considered dysplastic, while the 20-to-25-degree range is often called borderline.19PubMed Central. Radiographic Parameters of Adult Hip Dysplasia Other measurements examine the slope of the socket roof, the front-to-back coverage, and the position of the femoral head relative to the pelvic outline.20PubMed. Mild or Borderline Hip Dysplasia: Are We Characterizing Hips With a Lateral Center-Edge Angle Between 18° and 25° Appropriately?
Borderline dysplasia can be tricky to manage. A hip that looks almost normal on one X-ray view may reveal significant undercoverage when measured from a different angle or with a CT scan. That ambiguity means some borderline patients get dismissed as having “normal” hips when they are actually dealing with inadequate coverage and real cartilage stress.
Treatment in Infants
When dysplasia is caught early, treatment is usually non-surgical. The Pavlik harness is a soft brace that holds an infant’s hips in a flexed, spread-out position, encouraging the socket to deepen as the baby grows. Success depends on how severe the dysplasia is, how old the child is when bracing starts, and whether one or both hips are involved.21PubMed Central. Indicators of successful use of the Pavlik harness in infants with developmental dysplasia of the hip A study comparing standardized ultrasound monitoring during harness treatment to less structured follow-up found that the standardized approach raised success rates from 60% to 85%, mainly by preventing premature abandonment of the harness when the hip had not yet stabilized.22PubMed. Standardized In-harness Ultrasound Protocol Improves Success Rate of Brace Treatment for Dislocated Hips
If the harness fails or the diagnosis comes later, the next step is usually closed reduction under anesthesia, in which the surgeon manually guides the femoral head back into the socket and holds it there with a cast. One study of children who underwent successful closed reduction reported a rate of avascular necrosis (damage to the blood supply of the femoral head) of about 8%.23PubMed Central. Efficacy of closed reduction for developmental dysplasia of the hip: midterm outcomes and risk factors associated with treatment failure and avascular necrosis Across all DDH treatment methods, the rate of this complication ranges widely, from about 6% to nearly 48%, depending on the severity of the condition and the type of intervention.24PubMed Central. Avascular necrosis of the femoral head: Assessment following developmental dysplasia of the hip management That wide range reflects the reality that more severe cases requiring more aggressive treatment carry higher complication risks.
Pelvic Osteotomy in Children
In older children whose hip sockets did not remodel adequately on their own or with bracing, surgical reshaping of the pelvis becomes necessary. The bone around the socket is cut and repositioned to provide better coverage of the femoral head. These procedures are broadly grouped into redirectional osteotomies (which rotate the existing socket into a better position), reshaping osteotomies (which physically alter the socket’s shape), and salvage procedures (used when the original socket is too damaged to salvage by simply rotating it).25PubMed Central. Effects of different pelvic osteotomies on acetabular morphology in developmental dysplasia of hip in children The goal in every case is to spread the load over a larger area of cartilage and delay or prevent arthritis.26PubMed Central. Pelvic osteotomies in hip dysplasia: why, when and how? These osteotomies work by increasing the contact area between the socket and the femoral head, which relaxes the surrounding muscles and normalizes the forces passing through the joint.27PubMed. Pelvic osteotomies for the treatment of hip dysplasia in children and young adults
Adult Treatment Options
For adults, the decision tree splits based on how much cartilage damage has already occurred. Evidence for conservative management through exercise and education is growing but still limited.28PubMed. Understanding Adult Hip Dysplasia: Clinical Presentation, Assessment Techniques, and Exercise-Driven Management Strategies Strengthening the muscles around the hip can help stabilize the joint and redistribute forces, and there is at least case-level evidence that correcting postural habits can meaningfully reduce pain. One case report described a woman with mild dysplasia and a labral tear whose pain dropped substantially after postural correction and who returned to recreational running within a year.29PubMed Central. Postural correction reduces hip pain in adult with acetabular dysplasia: A case report That is just one person’s story, but it illustrates that not every dysplastic hip needs surgery.
When conservative measures are not enough and the cartilage is still in reasonable shape, the periacetabular osteotomy (PAO) is the main joint-preserving surgery for adults. The procedure cuts the bone around the socket in a controlled way and repositions it for better femoral head coverage. It can be done through a minimally invasive approach.30PubMed Central. Minimally invasive periacetabular osteotomy for adult hip dysplasia PAO does improve function, and it can be effective even in patients over 40, provided they have good function going in and no more than mild arthritis.31Journal of Bone and Joint Surgery. Periacetabular Osteotomy for Symptomatic Acetabular Dysplasia in Patients ≥40 Years Old
It is worth noting that even after PAO, the forces passing through the hip do not completely normalize. Modeling studies have shown that while contact stress improves, it often remains higher than in normal hips. In one study, the average contact stress in dysplastic hips during walking was roughly double that in normal hips, and after PAO it dropped but stayed significantly above normal.32PubMed Central. Joint Contact Stress Improves in Dysplastic Hips After Periacetabular Osteotomy but Remains Higher than in Normal Hips This suggests that PAO buys time and reduces symptoms, but it may not fully eliminate the mechanical disadvantage of a previously dysplastic hip.
Long-Term Outlook and Arthritis Risk
The big concern with dysplasia is early osteoarthritis. In a long-term follow-up of patients with symptomatic hip dysplasia who did not have surgery, about 20% developed osteoarthritis, and 11% eventually needed a total hip replacement. Higher body mass index and increasing age were the main predictors of who progressed to arthritis.33PubMed Central. Risk factors for long-term hip osteoarthritis in patients with hip dysplasia without surgical intervention Those numbers mean that the majority of people tracked in that study had not reached end-stage arthritis, but the risk is real and it is higher than in the general population.
When Hip Replacement Becomes Necessary
For dysplastic hips that have progressed to severe arthritis, total hip replacement (or arthroplasty) is the final option. The surgery is more technically challenging than a standard hip replacement because the anatomy is distorted. The socket may be shallow, misshapen, or missing bone where the implant needs to sit. The thighbone can be abnormally shaped or rotated. In the most severe cases, where the femoral head has been riding completely outside the socket for years, the surgeon may need to cut and shorten the femur to bring the hip back to its correct position without stretching the nerves.34PubMed. Challenges in Total Hip Arthroplasty in the Setting of Developmental Dysplasia of the Hip The acetabular component ideally goes into the true socket location rather than up where the femoral head has been sitting, but in some cases surgeons opt for a high placement depending on the available bone.35PubMed Central. Total Hip Arthroplasty in Patients with Crowe III/IV Developmental Dysplasia of the Hip: Acetabular Morphology and Reconstruction Techniques
These patients tend to be younger than typical hip replacement candidates, which raises its own concerns. Joint replacements do not last forever, and someone receiving one at 35 or 40 is more likely to need a revision surgery later in life than someone getting their first replacement at 70. This is one reason surgeons push hard to preserve the native hip with osteotomy when the cartilage still allows it.
Swaddling and Infant Positioning
One of the most actionable pieces of the DDH story involves how babies are positioned after birth. There is strong evidence linking traditional tight swaddling, where the legs are bound straight and pressed together, with higher rates of hip dysplasia. The same meta-analysis that quantified other risk factors found that swaddling carried roughly a sevenfold increase in risk.5PubMed. Risk factors of developmental dysplasia of the hip in infants: A meta-analysis based on cohort studies Populations that historically practiced this kind of leg-straight swaddling had higher DDH rates, and some that shifted to “hip-safe” swaddling, which allows the legs to spread and flex naturally, saw their rates drop.36PubMed Central. Developmental Dysplasia of Hip and Post-natal Positioning: Role of Swaddling and Baby-Wearing
Baby carriers that hold the infant’s legs in a frog-like position, with hips flexed and spread apart, are considered optimal for hip development. The practical takeaway for parents is straightforward: swaddling the upper body for comfort is fine, but the legs should always be free to move and bend at the hips. If you use a carrier, one that supports the baby’s thighs out to the knees and keeps the knees below the hips is preferable to one that lets the legs dangle straight down.
Why the Pelvis Is Vulnerable in the First Place
The human pelvis has been under conflicting evolutionary pressures for millions of years. Walking upright reshaped the pelvis into a bowl-like structure suited for supporting the trunk and transferring load to the legs, but childbirth requires the pelvic opening to be wide enough for a large-brained infant’s head to pass through. These competing demands, along with thermoregulation needs, have created a pelvis that is a compromise rather than an optimized structure for any single function.37PubMed Central. The evolution of the human pelvis: changing adaptations to bipedalism, obstetrics and thermoregulation The difficulties inherent to bipedal birth may trace back millions of years.38Continence Reports. Bipedalism and pelvic floor disorders, an evolutionary medical approach The hip socket’s shape at birth represents a work in progress, and when genetic susceptibility meets the wrong mechanical environment in utero or after birth, the compromise tips into dysplasia. It is one of the costs of being the only fully bipedal primate.