Femoroacetabular Impingement (FAI)

Femoroacetabular impingement (FAI) is a condition characterized by extreme friction in the hip joint due to bony irregularities. The femoral head and acetabulum rub against each other creating damage, pain and decreased range of hip motion. The damage can occur to the articular cartilage (the smooth white surface lining the bone ends) or the labrum (tissue lining the edge of the socket) during normal movement of the hip. The articular cartilage or labral tissue can fray or tear after repeated friction. Over time, more cartilage and labrum is lost, until eventually, the femur and acetabulum rub on each other, leading to arthritis.

FAI impingement generally occurs as two forms: 

Cam impingement

The cam form of impingement occurs 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 occurs when the rim of the socket or acetabulum has overgrown and is too deep. It covers too much of the femoral head, resulting in the pinching of the labral cartilage. The pincer form of impingement may also be caused when the hip socket is abnormally angled backward, 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

Symptoms of femoroacetabular impingement can include the following:

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

Risk factors

A risk factor is something that is likely to increase a person’s chance of developing a disease or condition. Risk factors for developing femoroacetabular impingement may include the following:

  • Athletes such as football players, weightlifters and hockey players
  • Heavy laborers
  • 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


Hip conditions should be evaluated by an orthopaedic hip surgeon for proper diagnosis and treatment. The doctor will perform the following to diagnose FAI:

  • Medical history
  • Physical examination
  • Diagnostic studies including X-rays, MRI scan and CT scan

Treatment options

Conservative treatment options refer to the management of the problem without surgery. Nonsurgical 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.

Conservative treatment measures

The conservative treatment measures include:

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

Surgical treatment

Hip arthroscopy to repair femoroacetabular impingement is indicated when conservative treatment measures fail to provide relief to the patient.