What is femoroacetabular impingement?

Femoroacetabular impingement (FAI), also called hip impingement, is a condition where the femoral head and the hip socket don't match appropriately, which can lead to premature contact between these two structures when the hip is placed in certain positions. Over time, this repeated contact can cause damage to the labrum (O-ring type structure which surrounds the hip socket) or the underlying cartilage.

Symptoms of hip impingement

Some people with FAI can live active lives and never experience pain or hip problems. Others, especially athletic and active people, may develop pain in the hip or thigh that is usually worse in a seated position. Clicking, popping or a pinching sensation may be felt deep in the hip joint.

Diagnosis

A diagnosis of FAI may be suspected after a detailed history and physical examination. X-rays can help evaluate the shape of the ball and socket to look for possible causes of impingement. The findings on X-ray are often subtle, however, and may be missed by practitioners who are unfamiliar with the condition.

Advanced imaging helps our doctors better understand what’s going on deep inside your hip socket. We may recommend specialized advanced imaging studies, which are all available at CHOP:

• 3-D reformatting imaging — computed tomography (CT) scans that combine X-rays and computer technology to create three-dimensional models of the hip anatomy
• Delayed gadolinium-enhanced MRI of cartilage (dGEMRIC) — imaging where an MRI scan is dedicated to detecting early cartilage breakdown and allows mapping of areas of early osteoarthritis or focal cartilage injury
• Radial hip reconstruction — MRI reconstruction technique that takes slices of the hip joint circumferentially around the ball and socket and allows for more accurate identification of areas of potential femoracetabular impingement compared to conventional radiography

Treatment for FAI/hip impingement

Treatment may include non-surgical options such as activity modification, physical therapy, injections and anti-inflammatory medications. For those patients that don’t respond to non-operative treatment, hip arthroscopy or a surgical dislocation of the hip may be recommended.