Introduction
Developmental dysplasia of the hip, often abbreviated as DDH, is diagnosed by combining clinical examination with imaging and, in some cases, follow-up observation over time. The condition involves abnormal development of the hip joint, ranging from a shallow acetabulum to partial or complete displacement of the femoral head from the socket. Because the joint may be unstable at birth or may fail to mature normally during infancy, the diagnostic approach depends heavily on the patient’s age and the degree of joint abnormality.
Accurate diagnosis matters because DDH can affect how the hip forms, how the child learns to bear weight, and how the joint functions later in life. When recognized early, treatment can often guide the hip into a normal position and promote proper development. If the diagnosis is delayed, the abnormal mechanics can lead to gait problems, leg-length inequality, pain, and premature osteoarthritis. For that reason, medical professionals aim not only to identify obvious dislocation, but also to detect subtle instability or delayed socket development before permanent damage occurs.
Recognizing Possible Signs of the Condition
DDH may be suspected from findings during routine newborn screening, from parental concern, or from signs that appear later in infancy or childhood. In newborns, the condition is often clinically silent, which is why careful examination is important even when no symptoms are reported. A hip may be unstable without causing pain or visible distress.
Clinical clues in infants can include unequal skin folds on the thighs or buttocks, one leg appearing shorter than the other, or limited abduction of the hip when the legs are gently opened. A doctor may also notice asymmetry in how the thighs move or a subtle sense that the hip is not seated normally in the socket. In some cases, a click is heard or felt during movement, although not every click indicates DDH and not every case of DDH produces a click.
As children get older, the signs become more functional. A toddler may walk with a limp, sway the trunk to one side, or show a waddling gait if both hips are affected. If only one hip is involved, the child may appear to favor one leg or stand with pelvic tilt. In older children and adults with undiagnosed DDH, hip pain, reduced range of motion, fatigue with walking, or early arthritis may become the reason for evaluation.
Medical History and Physical Examination
The diagnostic process begins with a detailed medical history. Clinicians ask whether DDH was present in the family, whether there were problems during pregnancy or delivery, and whether the baby was in a breech position. Breech presentation is a recognized risk factor because fetal position can influence how the hip develops in the womb. Doctors also ask whether the baby was the firstborn, whether there was oligohydramnios, and whether swaddling practices may have kept the hips tightly extended and adducted, which can contribute to instability in susceptible infants.
During the physical examination, the examiner evaluates both hips carefully and compares them with each other. In a newborn or young infant, the key goal is to detect instability rather than pain. Clinicians may perform maneuvers designed to assess whether the femoral head can be displaced from or reduced into the socket. The Ortolani maneuver checks whether a dislocated hip can be gently returned into the acetabulum, often producing a palpable or audible clunk. The Barlow maneuver tests whether a hip can be provoked to dislocate by gentle posterior pressure. These tests are performed carefully because forceful manipulation is not appropriate.
As infants grow, these maneuvers become less useful and other findings gain importance. Limited hip abduction, pelvic asymmetry, limb-length discrepancy, and abnormal gait patterns become more informative. Clinicians may measure the range of motion, inspect for asymmetrical folds, and assess how the child bears weight. A complete examination also looks for associated neuromuscular or syndromic conditions, because DDH is more common in children with generalized ligamentous laxity, torticollis, clubfoot, or certain genetic syndromes.
Diagnostic Tests Used for Developmental Dysplasia of the Hip
Imaging is the main tool used to confirm DDH and define its severity. The choice of test depends strongly on age. In early infancy, the femoral head is still largely cartilaginous, so plain X-rays may not show the joint clearly. For that reason, ultrasound is the preferred study in young babies, usually in those under about 4 to 6 months of age, when the cartilage and soft tissue structures can be visualized well.
Hip ultrasound can show whether the femoral head is centered in the socket, how deep the acetabulum is, and whether the joint is stable during gentle movement. It also helps assess the shape of the cartilaginous roof of the acetabulum and whether the femoral head is covered adequately. Dynamic ultrasound can reveal instability that is not apparent when the hip is at rest. This makes it especially useful when the physical examination is equivocal or when a newborn has risk factors but no obvious dislocation.
After the femoral head begins to ossify, usually later in infancy, plain radiographs become more informative. X-rays can demonstrate acetabular shallowness, lateral displacement of the femoral head, disruption of alignment lines, and delayed ossification of the femoral head. Radiographic measurements such as acetabular angle and the position of the femoral head relative to reference lines help quantify abnormal development. In older children and adults, radiographs are central to diagnosis because they show bony anatomy clearly and can reveal secondary degenerative change.
In more complex cases, magnetic resonance imaging may be used to assess the relationship between the femoral head and acetabulum, particularly after reduction or before surgery. MRI can show cartilage, labrum, and surrounding soft tissue structures that are not as well seen on X-ray. This is useful when doctors need to confirm whether the hip is truly centered, evaluate obstacles to reduction, or examine postoperative position without radiation exposure. Computed tomography is less commonly used because of radiation, but it may help in selected cases where detailed three-dimensional bony anatomy is needed.
Laboratory tests are not used to diagnose DDH directly, because the condition is structural rather than inflammatory or infectious. However, blood tests may be ordered if the clinical picture suggests a different diagnosis, such as infection, inflammatory disease, or a metabolic disorder affecting bone health. In those situations, laboratory studies do not confirm DDH itself, but they help exclude other causes of limp, pain, or limited motion.
Functional testing is also part of the evaluation, especially in older children. Doctors observe walking, standing balance, and the mechanics of hip motion. Gait assessment can reveal Trendelenburg sign, trunk lean, short stride, or compensatory movements that suggest instability or inadequate hip containment. These observations do not replace imaging, but they help determine how the abnormal anatomy is affecting function.
Tissue examination is not a routine part of diagnosis. It may become relevant only in surgical cases, when tissue obtained during reduction or reconstruction is examined to understand the anatomy of the joint or to identify interposed soft tissue blocking reduction. This is not typically needed to establish DDH, but it can contribute to treatment planning in difficult cases.
Interpreting Diagnostic Results
Doctors interpret DDH testing by considering both anatomy and stability. A normal newborn exam and normal ultrasound indicate that the hip is centered and developing appropriately, although follow-up may still be recommended in infants with strong risk factors. A hip that can be dislocated on examination or appears unstable on dynamic ultrasound is considered abnormal even if the baby has no symptoms. Instability suggests that the socket is not adequately containing the femoral head, which can interfere with normal shaping of the acetabulum.
On imaging, a shallow acetabulum, partial uncovering of the femoral head, or complete dislocation supports the diagnosis. In infants, the severity can range from mild acetabular immaturity to frank dislocation. The more displaced the femoral head and the less coverage it has, the greater the concern that normal joint development will not occur without treatment. Doctors also look for symmetry. A unilateral abnormality can be easier to miss clinically, but imaging may reveal one hip lagging behind the other in development.
Interpretation is always tied to age. A mildly shallow socket in a very young infant may represent developmental immaturity that could improve, while the same finding in an older infant may be more concerning. Likewise, an X-ray that appears normal in a newborn may not exclude DDH because the relevant structures are largely cartilaginous and not yet visible. For that reason, clinicians rely on age-appropriate imaging and may repeat studies over time if the diagnosis remains uncertain.
Conditions That May Need to Be Distinguished
Several other conditions can look similar to DDH or produce overlapping signs. In newborns, benign hip clicks are common and may occur without any instability or structural abnormality. A click alone is not enough to diagnose DDH. Clinicians differentiate this from true instability by assessing whether the hip actually dislocates or remains reduced under examination and by using imaging when needed.
Hip pain or limping in older children may be caused by transient synovitis, septic arthritis, Legg-Calve-Perthes disease, slipped capital femoral epiphysis, neuromuscular disorders, or limb-length discrepancy from other causes. These conditions are separated from DDH by history, physical findings, and imaging patterns. For example, septic arthritis usually presents with fever, pain, and refusal to bear weight, while DDH more often causes mechanical asymmetry or gait changes without systemic illness. Slipped capital femoral epiphysis typically occurs in adolescents, not infants, and has a very different radiographic appearance.
Some skeletal dysplasias and syndromic conditions can include hip abnormalities as part of a broader pattern. In these cases, the diagnosis of DDH may still be correct, but it must be understood in the context of an underlying disorder. A comprehensive examination is important when the hip findings are accompanied by unusual facial features, generalized joint laxity, abnormal stature, or other congenital anomalies.
Factors That Influence Diagnosis
Age is one of the most important factors affecting diagnosis. In the newborn period, physical examination and ultrasound are most useful. After a few months, radiographs become more reliable because ossification has begun. The diagnostic threshold also changes with age, because persistent dysplasia becomes more clinically significant as the hip matures and begins to bear weight.
Severity influences how obvious the condition appears. Mild acetabular dysplasia may be difficult to detect on physical examination and may only become apparent on imaging. By contrast, a complete dislocation is usually easier to recognize because the femoral head sits outside the socket and the leg may be shortened or abducted less well. Bilateral disease can also be harder to notice because symmetry may mask the discrepancy.
Associated medical conditions can complicate the diagnosis. Generalized ligamentous laxity can make the hips feel unstable in a way that overlaps with normal newborn flexibility, while neuromuscular conditions can alter posture and gait in ways that resemble hip pathology. Prior treatment, such as swaddling or bracing, may change the appearance of the joint on later studies. In addition, the experience of the examiner matters, because newborn hip assessment requires careful technique and interpretation.
Conclusion
DDH is diagnosed by integrating risk assessment, physical examination, and age-appropriate imaging. Clinicians look for subtle instability in newborns, restricted motion or asymmetry in infants, and gait changes or pain in older patients. Ultrasound is the main confirmatory test in early infancy, while X-rays become more useful as the femoral head ossifies. MRI and other studies may be used in selected complex cases, but they are not routinely required.
The diagnostic process is designed to identify not only obvious dislocation, but also the more common and more easily overlooked forms of hip dysplasia and instability. By interpreting examination findings together with imaging results and patient age, medical professionals can determine whether the hip is developing normally, mildly dysplastic, or significantly displaced. That combined assessment is what allows DDH to be recognized accurately and managed before long-term joint damage develops.