Femoroacetabular Impingement

What is Femoroacetabular Impingement?

Femoroacetabular impingement (FAI) is a condition characterised by excessive friction in the hip joint from the presence of bony irregularities. These cause pain and decreased range of hip motion. 

The femoral head and acetabulum rub against each other, causing damage and pain to the hip joint. The damage can occur to the articular cartilage (the smooth white surface of the ball or socket) or the labral tissue (the lining of the edge of the socket). The articular cartilage or labral tissue can fray or tear after repeated friction. Over time, more cartilage and labrum are lost until eventually the femur and acetabulum impact on one other. Bone-on-bone friction is commonly referred to as osteoarthritis.

Types of Femoroacetabular Impingement

FAI impingement generally occurs as two forms:  

• Cam impingement: The Cam form of impingement is when the femoral head and neck are not perfectly round, most commonly due to excess bone that has formed. This lack of roundness and excess bone causes abnormal contact between the surfaces.
• Pincer impingement: The Pincer form of impingement is when the socket or acetabulum rim has overgrown. It covers too much of the femoral head, resulting in the labral cartilage being pinched. The Pincer form of impingement may also be caused when the hip socket is abnormally angled backwards, causing abnormal impact between the femoral head and the rim of the acetabulum.

Most diagnoses of FAI include a combination of the Cam and Pincer forms.

Symptoms of FAI

The symptoms of the femoroacetabular impingement can include the following:

Pain, which may be described as a dull ache or sharp pain

• Pain in the inner hip or groin area after prolonged sitting or walking
• Groin pain associated with hip activity
• Complaints of pain in the front, side or back of the hip
• Pain in the buttocks or outer thigh area
• A locking, clicking or catching sensation in the hip
• Difficulty in walking uphill
• Restricted hip movement
• Low back pain

Risk Factors for the Development of FAI

A risk factor is something that is likely to increase your chances of developing a disease or condition. The risk factors for developing femoroacetabular impingement may include the following:

• Athletes such as football players, weightlifters and hockey players
• Workers engaged in heavy labour
• Repetitive hip flexion
• Congenital hip dislocation
• Anatomical abnormalities of the femoral head or angle of the hip
• Legg-Calves-Perthes disease: a form of arthritis in children where blood supply to the bone is impaired causing bone breakdown
• Trauma to the hip
• Inflammatory arthritis

Diagnosis of FAI

FAI is diagnosed based on your medical history, a physical examination and diagnostic studies, including X-rays, MRI scans and CT scan.

Treatment Options for FAI

Non-surgical management of FAI will probably not change the underlying abnormal biomechanics of the hip causing the FAI but may offer pain relief and improved mobility. These conservative treatment measures include:

• Rest
• Activity modification and limitations
• Anti-inflammatory medications
• Physical therapy
• Injection of steroid and analgesic into the hip joint

The surgical treatment for FAI includes hip arthroscopy, which is indicated when conservative treatment measures fail to provide relief.