Hip Impingement (FAI)

Cam Impingement

The hip is a ball and socket joint. The ball is spherical, attached to the top of the femur (thigh bone) by the femoral neck. The femoral neck is usually slim to allow a good range of motion in the joint.

Healthy Hip Joint

Some patients are born with or develop a swelling or 'Cam' deformity on the ball (illustrated below) and/or on the femoral neck.

Hip with a Cam Impingement

Deformity of the spherical ball can result in an oval shape that fails to fit in the socket correctly causing damage to the hip with movement. The femoral neck is wider than usual; this reduces the range of movement in the hip and causes impingement or catching within the joint (see video clip below).

A 'Cam' deformity is often associated with a 'Pincer' deformity (see below) resulting in a 'Mixed Picture' impingement.

 

Pincer Impingement

The hip is a ball and socket joint. The socket is essential to the optimal performance of the joint. The majority of the socket is made from bone with an articular cartilage surface but also is deepened by the labrum. In most individuals the position of the socket is such that the ball is stable within the socket, distributes load evenly and provides a good range of movement.

Patients with Pincer impingement have a deep socket and patients with a shallow socket have Hip Dysplasia. Range of movement of the hip is reduced with a deep socket or 'Pincer' (illustrated below).

Hip wih a Pincer Impingement

The femoral neck impinges or abuts on the rim of the socket often causing a Labral Tear or articular cartilage damage (see video clip below).

In young adult life the body can compensate for the damage caused by these conditions. Patients may have minimal symptoms of mild pain after exercise or restriction in range of movement of their hip or hips noticed for example by the inability to sit crossed legged. Over time the symptoms can restrict activities such as running, sitting for prolonged periods and getting out of a car. Sometimes an injury to the hip can precipitate a Labral Tear with a subsequent sudden deterioration of symptoms.

 

Mixed Picture Impingement

It is common for patients to have both 'Cam' and 'Pincer' deformities. This is referred to as a 'Mixed Picture' Impingement. It is important that both deformities are looked for and corrected at the time of Hip Arthroscopy.