Femoral Acetabular Impingement (FAI)
Hip pain and injury are common ailments of athletes, dancers and older adults, which can limit athletic participation or even activities of daily living. For many years young active patients complaining of hip pain and injury were diagnosed with a pulled muscle or a groin strain. Over the last 10-15 years a new understanding of hip impingement has evolved and is now recognized as a common cause of hip pain. Hip impingement is pinching between the ball and socket, leading to pain and injury of soft tissue around the socket.
Femoroacetabular impingement (FAI) refers to pinching between the femur (thigh bone) and the acetabulum (hip socket). Extra bone just below the head of the femur (cam lesion), or over coverage of the socket (pincer lesion) can cause impingement. The body’s response to impingement is inflammation, tightening of the hip capsule and compensatory strain to muscles around the hip. Therefore patients often complain of pain around the front, side or back of the hip in addition to deep groin pain. When pinching persists, it causes damage to the labrum (fibrocartilage forming a ring around the socket like a gasket), which can eventually tear. A torn labrum can lead to catching or popping, and eventually damage of the joint cartilage (smooth gliding surface lining joints).
The most common symptom of FAI is deep groin pain with certain activities such as twisting, turning or squatting. As the condition progresses pain is elicited with more subtle activities such as prolonged sitting or walking.
Orthopaedic surgeons trained in hip arthroscopy and FAI can make the diagnosis of FAI by examining the hip and performing x-rays. MRI is appropriately used for operative planning. MRI’s are often ordered prematurely. It is a common misconception that if the radiologist reports no labral tear on MRI that the patient does not have FAI. Even if there is not a frank detached tear of the labrum on MRI, labral bruising and injury is seen in surgery. It is preferable to treat FAI early before labral tearing and cartilage injury occurs. Initial treatment includes physical therapy, anti-inflammatories and steroid injections. If these measures fail, arthroscopic surgery is offered to shave down the excess bone and repair the labrum.