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Femoral Acetabular Impingement

What is Femoral Acetabular Impingement?

The hip joint is a classic ball and socket joint consisting of the femoral head (ball) of the femur which is the long bone in your upper leg, and the acetabulum (the socket) which is made from the three bone in the pelvis. Femoral acetabular impingement (FAI) is a hip condition where either or both the femoral head (ball) and the acetabular rim (socket) develop bone growth lesions due to abnormal joint contact and pinching of the soft tissue around the joint. The extra bone on the femoral head and neck is typically called a cam shaft lesion, while the buildup of bone on the acetabular rim is often called pincher lesion. Along with the boney lesions in FAI, quite often there may be a tear in the labrum around the acetabulum as well.

What Causes FAI?

There are several factors that can lead to FAI, including a developmental and body type component, as well as a traumatic and improper training component. Sometimes the socket may develop too deep in the hip during adolescence, or increased anteversion in the hip joint. Repetitive hip motions and extreme range of motion activities such as gymnastics and ice hockey may make one susceptible to FAI. Often it is a combination of both anatomical abnormalities and activity related motions that cause FAI.

What are the Signs and Symptoms of FAI?

People with FAI often report pain in the groin area of the hip. They often describe it as a deep ache which gets worse with activity. The pain mostly occurs with hip flexion and internal rotational motions (ice skating or swinging a bat), although any extreme range of motion can aggravate symptoms. A common sign people will show a doctor is the “C” sign. The person will grab their hip with their thumb on the outside of the hip and the fingers in the groin region. They will say that the fingers are where the pain is. The onset of the pain is usually gradual and increases with activity and decreases with rest. It usually has been present for some time and is often thought of as a muscle strain at first.

Diagnosis of FAI

A positive diagnosis of FAI starts with a good physical exam by an orthopedic surgeon or physical medicine doctor. Your doctor should review your history of hip pain; noting when it comes on, where it is, and how long it has been going on for.  Most manual tests of the hip are not specific enough to definitively diagnose FAI. Since FAI is a boney condition, X-rays are used to confirm the physical exam findings by the doctor. The doctor may order a MRI to diagnose any labral or soft tissue damage.

Treatment Options

Conservative management of FAI should consist of activity modification to limit the repetitive contact occurring in the hip joint. Physical therapy may be helpful to restore range of motion and strength in the joint. Anti-inflammatory medications may also help manage the pain and stiffness in the hip.

Surgical intervention is the only way to truly alleviate the boney impingement.  Without surgery, the impingement could lead to more degeneration and pain in the hip, requiring a total hip replacement. Nowadays, this is usually done arthroscopically to minimize additional trauma to the hip, and maximize healing and recovery. Physical therapy afterwards should focus on regaining range of motion of the hip, especially the hip flexors and groin muscles. Physical therapy should also emphasize strengthening the muscles around the hip and pelvis.