Hip dysplasia is a structural condition where the hip joint is improperly formed. The cup-shaped hip socket, called the acetabulum, is too shallow or incorrectly oriented to fully cover the ball of the thigh bone, known as the femoral head. This poor fit causes the hip to be unstable and allows the ball to shift within the socket. Although often described as a pediatric issue, mild forms may not cause symptoms until years later, leading to a diagnosis in adolescence or adulthood. The delayed manifestation in adults is typically a result of accumulated mechanical stress on the joint over time.
Understanding Adult Hip Dysplasia
The anatomical defect centers on the acetabulum failing to provide adequate coverage for the femoral head. The lack of a deep, well-formed socket means a smaller surface area is available to bear the body’s weight. This condition in adults is most often the residual effect of developmental dysplasia of the hip (DDH), which was either undiagnosed or not fully corrected during childhood.
The biomechanical consequence of this shallow socket is the concentration of load onto a smaller area of the joint cartilage. This abnormal distribution of force leads to accelerated wear and tear on the joint’s smooth lining, the articular cartilage. The increased shear forces also frequently cause damage to the labrum, the ring of cartilage that rims the acetabulum. Over time, this accelerated degeneration results in early-onset osteoarthritis, which is the primary source of pain in adult hip dysplasia.
Recognizing the Symptoms in Adulthood
The most common symptom prompting medical attention is pain, typically localized to the groin area or the anterior hip. This pain is often aggravated by physical activity, such as walking, running, or prolonged standing, and may radiate down the front of the thigh. Since the condition causes progressive joint damage, the intensity and frequency of the pain generally increase over many years, sometimes leading to a noticeable limp or changes in walking pattern.
Patients frequently report mechanical symptoms, often indicative of a labral tear or joint instability. These sensations include clicking, popping, or catching within the hip joint during movement. A feeling of the hip “giving way” or general instability is another symptom, especially during weight-bearing activities. Because these symptoms can mimic other common hip injuries, adults with hip dysplasia often experience a significant delay in receiving a correct diagnosis.
Methods of Diagnosis
The diagnostic process begins with a thorough physical examination, which includes assessing the patient’s gait, range of motion, and specific maneuvers to test for hip instability. However, a definitive diagnosis relies on medical imaging to evaluate the bony anatomy of the joint. The standard method for diagnosis is a plain X-ray of the pelvis, taken from the front (anteroposterior or AP view).
The X-ray allows the physician to measure specific angles that quantify the degree of acetabular coverage. The most commonly used measurement is the lateral center-edge angle (LCEA), which assesses the lateral coverage of the femoral head. A normal LCEA value is typically greater than 25 degrees in adults, while a measurement less than 20 degrees is considered diagnostic for hip dysplasia. Hips between 20 and 25 degrees are sometimes classified as “borderline dysplasia,” indicating a subtle insufficiency.
Advanced imaging, such as Magnetic Resonance Imaging (MRI) or Computed Tomography (CT) scans, may be used to further assess secondary damage. These scans are valuable for visualizing soft tissues like the labrum and the articular cartilage. They help determine the extent of cartilage loss and the presence of associated labral tears, which guides treatment decisions.
Treatment Pathways for Dysplasia
Treatment is determined by the patient’s age, the severity of the dysplasia, and the degree of arthritis developed in the joint. Non-surgical management is typically the first approach for mild cases or for managing symptoms when surgery is not necessary. This involves activity modification, often recommending lower-impact exercises like swimming or cycling. Physical therapy focuses on strengthening the muscles surrounding the hip joint for stability, and non-steroidal anti-inflammatory drugs (NSAIDs) can help manage pain. These measures do not correct the underlying mechanical problem of the shallow socket.
For patients with minimal to no advanced arthritis, a joint-preserving surgical option is often recommended. The procedure known as Periacetabular Osteotomy (PAO) involves surgically cutting the pelvic bone around the acetabulum and reorienting the socket to cover the femoral head more fully. This re-alignment restores a more normal distribution of forces across the joint, aiming to relieve pain and delay progression to end-stage osteoarthritis. PAO is most effective in younger adults, typically under age 40, who retain healthy cartilage.
When the hip joint has progressed to severe, end-stage osteoarthritis, the most reliable treatment for pain relief and functional improvement is Total Hip Arthroplasty (THA). This procedure, commonly known as a hip replacement, involves removing the damaged ball and socket and replacing them with artificial components. While PAO is favored for younger patients to preserve the natural joint, THA is the preferred option for older patients or those whose cartilage is too damaged.