Hip dysplasia is a condition affecting the hip joint, a ball-and-socket connection between the thigh bone and the pelvis. In a healthy hip, the rounded top of the thigh bone, known as the femoral head, fits securely into a cup-shaped socket in the pelvis, called the acetabulum. When hip dysplasia occurs, this joint does not develop properly. The socket might be too shallow, or the ball might not be positioned correctly within it, leading to a loose or unstable connection.
Prevalence Across Populations
Hip dysplasia, particularly Developmental Dysplasia of the Hip (DDH), varies in prevalence across different age groups and populations. In infants, this condition is the most frequently encountered pediatric hip issue, affecting approximately 1% to 3% of newborns globally. While 1 to 3 out of every 1,000 live births are diagnosed with a dislocated hip, a larger proportion, around 15 to 20 per 1,000, experience some hip instability. A review of infant studies indicates a pooled prevalence of about 1.40%.
The incidence of DDH shows geographical and ethnic variations. For instance, reported rates range from 0.06 per 1,000 live births in some African populations to 76.1 per 1,000 in Native American communities. Within Europe, the incidence fluctuates from 0.59 to 27.53 per 1,000 live births, demonstrating regional differences. These discrepancies often stem from variations in diagnostic criteria, examination methods, and healthcare professional skill.
Beyond infancy, hip dysplasia can persist or manifest later in adulthood, sometimes without prior diagnosis. Studies indicate the overall prevalence of radiographic hip dysplasia in the general asymptomatic adult population is about 2.3%. This rate is higher in females, affecting approximately 3.8% compared to 2.7% of males. Such undiagnosed or mild cases contribute to hip pain and are a leading cause of hip arthritis in individuals under 50 years old, accounting for many total hip replacements. A large-scale Chinese survey found the adult prevalence to be 1.52%, with women showing a higher rate at 2.07% versus 0.75% in men.
Factors Influencing Its Occurrence
Several factors contribute to hip dysplasia, including genetic and environmental influences. A genetic predisposition exists, as the condition often runs in families. If a parent has a history of hip dysplasia, their child’s risk increases by about 12%. A child with an affected sibling also faces a higher likelihood, around 6%, of developing the condition. This suggests a multifactorial inheritance pattern rather than a simple genetic cause.
Biological sex plays a role, with girls being disproportionately affected; they are two to four times more likely to develop hip dysplasia than boys. The baby’s position in the womb is another influential factor, particularly breech presentation, where the baby is positioned feet or bottom first. This can lead to increased pressure on the hips, especially during the third trimester, and is a risk indicator. First-born children tend to have a higher incidence, potentially due to the uterus being less stretched, creating a tighter environment.
Post-natal care practices, such as swaddling, can also influence hip development. Improper swaddling, which involves tightly wrapping a baby’s legs straight and pressed together, restricts natural hip movement and can contribute to dysplasia. Conversely, hip-healthy swaddling allows the baby’s hips to bend up and out, mimicking the natural fetal position and promoting proper joint formation. Other factors include oligohydramnios, or low amniotic fluid levels, which can limit fetal movement and space within the womb.
The Role of Screening in Detection
Screening practices play a role in determining the reported prevalence of hip dysplasia. For infants, initial detection involves physical examinations, such as the Ortolani and Barlow maneuvers, performed by healthcare providers. These gentle tests assess for hip instability and are standard until approximately six months of age. If an abnormal finding or risk factors are present, ultrasound imaging is employed to visualize the hip joint’s structure and confirm the diagnosis.
The extent of screening can directly influence prevalence data. Countries with universal ultrasound screening programs, where all infants are examined, report higher rates of hip dysplasia compared to those with selective screening, which focuses only on high-risk cases. While universal screening identifies more instances of dysplasia, including mild forms that might resolve spontaneously, it also carries the potential for overtreatment. Less comprehensive screening, conversely, can lead to an underestimation of the condition’s true occurrence, as many cases might go undiagnosed until later in life.
Early detection of hip dysplasia is important for favorable outcomes. When identified promptly, particularly in infancy, non-surgical interventions like specialized harnesses are successful in guiding proper hip development. This early intervention reduces the need for invasive surgical procedures in childhood or adulthood. Timely diagnosis helps prevent long-term complications such as early-onset osteoarthritis, chronic hip pain, and mobility limitations.