The hip joint is a ball-and-socket joint consisting of the femoral head (ball) of the femur, and the acetabulum (the socket), made from the three bones of the pelvis. Femoroacetabular impingement (FAI) is a hip condition where either or both the femoral head (ball) and the acetabular rim (socket) are abnormally shaped, resulting in abnormal joint contact, pinching of the soft tissue around the joint, and damage to the labrum (a cartilage ring around the hip socket) and joint cartilage. The abnormal bone shape on the femoral head and neck is typically called a cam lesion, while the abnormal orientation or depth of the acetabulum is typically called a pincer lesion. Along with the bony lesions in FAI, quite often there may be a tear in the labrum around the acetabulum and delamination of the adjacent joint cartilage.
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 there may be increased anteversion in the hip joint. Repetitive hip motions and extreme range of motion activities such as ballet, soccer, 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.
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 (such as ice skating or swinging a bat), although any extreme range of motion can aggravate symptoms. Squatting and/or sitting may be uncomfortable. Symptoms can also include the sensation of catching or locking. 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, increasing with activity and decreasing with rest. It usually has been present for some time and is often thought of as a muscle strain at first.
A positive diagnosis of FAI starts with a 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 bony condition, X-rays are used to supplement the physical exam findings by the doctor. The doctor may order an MRI to diagnose any labral or soft tissue damage. This frequently is done with injection of contrast dye into the joint to better assess the joint cartilage and possible labral tears. Typically an image-guided intra-articular injection will be ordered as well to further assess the source of hip pain. Perceived hip pain sometimes can be referred from the spine or surrounding soft tissues. The injection can help to differentiate the source of pain. Should the findings suggest the spine as the source of pain, a referral to one of the physiatrists as part of our interdisciplinary team will likely be recommended.
Conservative management of FAI should consist of activity modification to limit the repetitive contact occurring in the hip joint. Physical therapy often is helpful to improve 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 indicated if non-operative measures should fail. The goal would be to restore a normal anatomic relationship and surgically treat the labral tear. Addressing the labral tear is typically done by repair, but may require debridement or reconstruction. Without surgery, the impingement could lead to more degeneration and osteoarthritis with pain in the hip, possibly resulting in the need for a total hip replacement. Nowadays, this is most frequently done arthroscopically to minimize additional trauma to the hip, and maximize healing and recovery. Sometimes the degree of bony abnormality may require open surgery with surgical dislocation and/or osteotomies. 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.