A cam deformity of the hip is an abnormal shape of the “ball” part of the hip’s ball-and-socket joint. It involves a bony overgrowth or bump on the femoral head, the top part of the thigh bone. This irregular shape can cause the hip joint to rub abnormally during movement, leading to discomfort and pain. It is a common cause of hip pain and impingement, particularly among active individuals.
The Anatomy of a Cam Deformity
The hip functions as a ball-and-socket joint, where the femoral head, a typically spherical structure, fits smoothly into the acetabulum, the cup-shaped socket of the pelvis. In a cam deformity, the femoral head is not perfectly round; instead, it possesses an extra bony prominence at the junction where the head meets the neck of the femur. This irregular shape disrupts the smooth gliding motion within the joint.
During certain hip movements, especially deep flexion or internal rotation, this bony bump can jam or “impinge” against the rim of the acetabulum. This repetitive mechanical rubbing and collision is known as femoroacetabular impingement (FAI). Over time, this repeated contact can cause significant damage to the articular cartilage and the labrum, a ring of fibrocartilage that deepens the hip socket and helps maintain joint stability.
Associated Symptoms and Risk Factors
Individuals with a cam deformity often experience a deep, aching pain in the groin or the front of the hip. This pain can range from a dull ache to a sharp, intense sensation and may sometimes extend to the side of the thigh or the buttocks. Stiffness and a reduced range of motion in the hip are also common symptoms, with some individuals reporting a clicking or popping sensation within the joint. Pain is frequently triggered by specific activities that involve deep hip flexion or rotation, such as prolonged sitting, squatting, or participating in pivoting sports.
The development of a cam deformity is often linked to adolescent growth spurts, particularly in young athletes. High-impact sports that involve repetitive hip flexion and rotation, like ice hockey, basketball, and soccer, are associated with a higher incidence of cam morphology. The mechanical stress placed on the developing growth plates during these activities is thought to contribute to the formation of the bony prominence. There is also evidence to suggest a genetic predisposition, with studies indicating an increased incidence among siblings.
How a Cam Deformity is Diagnosed
Diagnosing a cam deformity typically begins with a thorough physical examination. A healthcare provider will assess the hip’s range of motion and look for specific movements that reproduce the patient’s pain. A common orthopedic test performed is the FADIR test, which involves flexing the hip, bringing the leg across the body (adduction), and rotating it inward (internal rotation). If this maneuver elicits the patient’s characteristic groin pain, it suggests the presence of FAI.
Following the physical examination, imaging studies are used to confirm the diagnosis and visualize the bone structure. An X-ray is usually the initial imaging step, providing clear views of the femoral head’s shape and any bony overgrowth. An MRI or MR arthrogram, which involves injecting contrast dye into the joint, offers a more detailed view of soft tissues like the labrum and articular cartilage, allowing for the detection of any associated damage.
Non-Surgical Management
For many individuals, non-surgical management is the initial approach to treating a cam deformity. This conservative strategy primarily focuses on physical therapy, which aims to strengthen the muscles surrounding the hip and improve core stability. Therapists work on correcting movement patterns to reduce stress on the hip joint and improve overall biomechanics without causing impingement. Approximately 60% of patients with cam lesions can find successful symptom relief through these non-operative methods.
Activity modification is an important component, involving the avoidance of specific movements and high-impact activities that cause pain or exacerbate symptoms, particularly deep hip flexion and internal rotation. Nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen or naproxen, may be prescribed to help manage pain and reduce inflammation in the short term. In cases of persistent or severe inflammation, a corticosteroid injection directly into the hip joint can provide temporary pain relief, though it does not address the underlying mechanical issue.
Surgical Intervention
When conservative treatments do not adequately relieve symptoms, surgical intervention may be considered for a cam deformity. The standard procedure is typically a hip arthroscopy, which is a minimally invasive surgery. This technique involves making small incisions around the hip joint, through which a surgeon inserts a tiny camera and specialized instruments to view and operate within the joint.
During the arthroscopy, the primary goal is to perform an osteoplasty, also known as femoral head reshaping or cam resection. This involves carefully shaving down the excess bone on the femoral head-neck junction to restore its normal spherical shape, thereby eliminating the impingement. If the labrum or articular cartilage has been damaged due to the repetitive rubbing, repairs to these soft tissues are often carried out during the same arthroscopic procedure, aiming to restore proper joint mechanics and reduce further wear.