Femoroacetabular Impingement (FAI)

The hip joint’s ball-and-socket structure is engineered for stability and mobility. The femoral head, the rounded top of the thighbone, acts as the “ball.” The acetabulum, part of the pelvic bone, serves as the “socket.” Both the femoral head and the acetabulum are covered with articular cartilage, a smooth, slippery tissue that reduces friction during movement. This cartilage also helps absorb shock, protecting the bones from wear and tear.

Surrounding the acetabulum is the labrum, a ring of fibrocartilage. The labrum deepens the acetabulum, enhancing the stability of the joint. This additional depth helps the femoral head remain securely in place, especially during dynamic activities. The labrum also serves as a seal for the joint, maintaining the synovial fluid inside the joint capsule. This fluid lubricates the joint, further reducing friction and nourishing the articular cartilage.

The labrum is essential for maintaining hip stability, enhancing the range of motion, and ensuring proper alignment between the femoral head and acetabulum. In a well-functioning joint, the femoral head fits securely within the acetabulum. However, when the structures of the joint are irregularly shaped, friction can occur, leading to damage.

Femoroacetabular Impingement (FAI) is a condition characterized by abnormal contact between the hip bones, leading to joint damage. This occurs when the bones that form the hip joint develop abnormally, creating an irregular shape that causes them to rub against each other during movement. Over time, this friction can damage the labrum and articular cartilage, potentially leading to arthritis or other degenerative conditions if left untreated.

FAI can be classified into three main types:

1. CAM Type: In CAM-type FAI, the femoral head is not perfectly round. Instead, it has a bony protrusion or bump that grinds against the acetabulum during hip movements. This abnormal shape can cause significant damage to the labrum and the acetabular cartilage.
2. Pincer Type: In the pincer type of FAI, the acetabulum covers too much of the femoral head. This over-coverage results in excessive contact between the acetabulum and the femoral head, leading to pinching of the labrum and cartilage damage.
3. Combined Type: The combined type of FAI involves features of both CAM and pincer types. In this scenario, both the femoral head and the acetabulum contribute to the abnormal contact and subsequent joint damage.

The symptoms of FAI can vary but often include a combination of the following:

• Groin Pain: Often described as a deep ache or intermittent pain, groin pain is one of the most common symptoms of FAI. This pain typically worsens with activity and may be more pronounced after prolonged sitting or walking.
• Pain on the Outside of the Hip: Some individuals experience pain on the outer part of the hip, which can radiate down the thigh.
• Sharp Pain During Certain Movements: Activities that involve twisting, turning, or squatting can trigger sharp, stabbing pain in the hip joint.
• Dull Ache After Activity: After physical activity or long periods of immobility, a dull ache may develop in the hip.
• Clicking or Locking Sensations: FAI can cause a sensation of the hip joint clicking, catching, or even locking up during movement, indicating potential labral damage.
• Instability and Decreased Range of Motion: The hip may feel unstable, and the range of motion can be significantly reduced, making it difficult to perform everyday activities.
• Stiffness and Limping: Persistent stiffness in the hip can lead to a limp, affecting overall mobility and quality of life.

Diagnosing FAI requires a combination of a thorough clinical evaluation and imaging studies. Hip surgeon Dr. Mark Cinque will typically begin with a physical examination, assessing the patient’s range of motion, identifying pain points, and performing specific maneuvers, such as the FADIR test (flexion, adduction, and internal rotation). If this test elicits pain, it may indicate the presence of FAI.

Imaging tests are crucial for confirming the diagnosis and understanding the extent of the damage. X-rays can reveal the shape of the bones and the presence of any bony abnormalities. Magnetic Resonance Imaging (MRI) provides detailed images of the soft tissues, such as the labrum and cartilage, helping to identify tears or other damage.

In some cases, diagnostic injections of corticosteroids into the hip joint may be used. If the injection provides temporary relief from symptoms, it can help confirm that the pain is originating from the hip joint.