Femoroacetabular impingement (FAI) is a condition where the bones of the hip are abnormally shaped.
The hip is a ball-and-socket joint. The socket is formed by the acetabulum, which is part of the large pelvis bone. The ball is the femoral head, which is the upper end of the femur (thighbone).
A slippery tissue called articular cartilage covers the surface of the ball and the socket. It creates a smooth, low friction surface that helps the bones glide easily across each other.
The acetabulum is ringed by strong fibrocartilage called the labrum. The labrum forms a gasket around the socket, creating a tight seal and helping to provide stability to the joint.
Because they do not fit together perfectly, the hip bones rub against each other and cause damage to the joint.Evidence is emerging that subtle abnormalities around the hip, resulting in femoroacetabular impingement (FAI), may be a contributing factor in some instances to osteoarthritis in the young patient.
FAI is the abnormal contact or friction between the femoral neck/head (ball) and the acetabular margin (socket), causing tearing of the labrum and avulsion of the underlying cartilage region, continued deterioration, and eventual onset of arthritis.