Femoroacetabular impingement (FAI)

What is Femoroacetabular impingement (FAI)

In this condition there is abnormal contact between the ball and socket parts of the hip joint due to abnormal benign growths of bone which causes groin pain and can lead to damage to the joint.

There are two main types, although both can occur together:

Cam-type impingement – here the head and neck (“ball part”) of the joint has a prominent bump which abnormally contacts the socket in certain positions of the hip causing pain and subtle shearing movements and decentering of the axis of rotation of the hip (hence “cam” as in the cam of an engine).  When this occurs repetitively the hip and labrum  can be damaged and ultimately it is thought that this may lead to an increased risk of arthritis.

Pincer-type impingement – here abnormal extensions of bone from the edges of the socket protrude out (like the pincers of a crab) and abnormally contact the head and neck (“ball part”) of the joint causing pain and damage to the neck of the joint.

What are the symptoms?

The impingement can cause hip pain that is felt in the groin. This is often made worse by prolonged sitting or driving and with certain positions of the hip. If the impingement has caused a cartilage (labral) tear then clicking or catching can also be felt in the hip.

How is it treated?

Both types of impingement can be dealt with by open surgery, mini-open surgery or by key-hole surgery (hip arthroscopy) during which the abnormal growths are trimmed and the damage that has been caused is repaired.