Femoroacetabular Impingement (FAI) Overview
Femoroacetabular impingement (FAI) is a hip condition characterized by anatomic abnormalities of the bones of the hip joint during growth and development. The abnormal shape leads to decreased range of motion and mechanical impingement (pinching) of the soft tissue structures. Over time, chronic impingement can lead to degeneration and tearing of the hip labrum and cartilage. Santa Barbara, Goleta, Santa Maria and Ventura, California orthopedic hip specialist, Dr. Jervis Yau specializes in diagnosing and treating hip pathology due to impingement.
The hip is a ball and socket joint covered by articular cartilage that helps to distribute force and facilitate movement in a low friction environment. In patients affected by femoroacetabular impingement (FAI), the articular cartilage will gradually wear due to constant shearing forces from the abnormal boney anatomy. Along with articular cartilage injury, hip impingement can commonly lead to labral tears. The labrum is a circumferential structure of the hip that has a suction seal effect to enhance stability of the hip joint. Once torn, the hip looses stability and often leads to pain and dysfunction.
Are There Different Types of Hip Impingement?
Hip impingement may begin in adolescence and is a major cause of early degenerative joint disease in young, active patients.
There are three forms of femoroacetabular impingement (FAI):
- Pincer impingement: Extra bone of the acetabulum (socket) extends further than normal over the edge of the femoral head (ball), causing the socket to be too deep.
- Cam impingement: Abnormal bone formation at the femoral head and neck that contacts the acetabular rim when the hip is in flexion, adduction and internal rotation.
- Mixed impingement: Presence of both pincer and cam deformities leading to impingement.
What are Common Femoroacetabular Impingement (FAI) Symptoms?
It is unknown how many patients have hip impingement. Many patients will have the abnormality but not know because they are asymptomatic. When patients start having symptoms, it is likely due to progressive damage to the articular cartilage or labrum.
Femoroacetabular impingement (FAI) commonly causes patients to experience sharp, ongoing pain in the groin area, especially when the hip is flexed, adducted (towards midline) and internally rotated (turned in). Patients may also notice stiffness of the joint and pain that radiates to the outside of the hip or down the thigh.