Femoroacetabular impingement (FAI) occurs in the hip joint. Impingement refers to some portion of the soft tissue around the hip socket getting pinched or compressed. Femoroacetabular tells us the impingement is occurring where the femur (thigh bone) meets the acetabulum (hip socket). There are two different types of impingement. They differ slightly depending on what gets pinched and where the impingement occurs.
The first is called cam-type impingement. This occurs when the round head of the femur isn’t as round as it should be. It’s more of a pistol grip shape. It’s even referred to as a pistol grip deformity. The femoral head isn’t round enough on one side (and it’s too round on the other side) to move properly inside the socket.
The result is a shearing force on the labrum and the articular cartilage, which is located next to the labrum. The labrum is a dense ring of fibrocartilage firmly attached around the acetabulum (socket). It provides depth and stability to the hip socket. The articular cartilage is the protective covering over the hip joint surface.
Sometimes cam-type impingement occurs as a result of some other hip problem (e.g., Legg-Calvé-Perthes disease, slipped capital femoral epiphysis or SCFE). But most of the time, it occurs by itself and is the main problem. Men are affected by cam-type impingement more often than women.
Although we know a lot about the causes of this condition, what to do about it remains in question. Can it be prevented is the first question. Should we even try to prevent it is the next question.
Some people have abnormally shaped hips but don’t ever develop symptoms. It has been suggested that we need to figure out who is at risk for pain and other problems from FAI before launching into a prevention program for everyone.
On the other hand, if some easy screening tests were done to find those individuals who are at risk, then perhaps a careful wait-and-watch program would be helpful. Or maybe some simple changes in activity would be all that is needed. Preventing substantial changes in the hip and the need for surgery would be a worthy goal.
Conservative (nonoperative) care really requires early recognition. So, it’s a “catch-22” kind of situation. There’s no evidence that screening and prevention help but without catching the problem early, conservative care quickly gets replaced by a more invasive approach with surgery.