Femoroacetabular impingement (FAI) is a disorder of the hip where the bones of the ball and socket hip joint are abnormally shaped causing rubbing, irritation and damage to the joint. There are 3 types of abnormalities associated with a FAI disorder.
● A CAM impingement is an abnormality of the ball aspect of the femoral head (end of the thigh bone) where the head is not round and therefore cannot rotate smoothly within the acetabulum (socket).
● A pincer impingement is an abnormality of the acetabulum, typically due to an extra bony extension around the rim of the acetabulum (hip socket) resulting in a deeper socket, and can impinge on the femoral head.
● The third abnormality is a combination of the cam and pincer impingements where both deformities are present.
The abnormal shape associated with a FAI impingement results in damage to the articular cartilage (joint cartilage) and may result in early degenerative changes. FAI typically presents as pain in the anterior (front) aspect of the hip made worse with running, squatting, stopping, starting or sudden change of directions.