Femoroacetabular Impingement - FAI
What is Femoroacetabular Impingement?
The hip joint is a type of ball and socket joint which is made of the the femoral head (the top of the thigh bone which is shaped like a ball) and the acetabulum (part of the pelvis which forms a socket for the ball to sit in). 
Femoroacetabular Impingement (also shorted to FAI) occurs when either the ball or the socket are abnormally formed.
This results in the ball and socket rubbing abnormally against each other. This causes the hip joint to wear out, causing damage to structures that are important to the proper function of the hip such as:
- cartilage damage
- labral tears
- ligamentum teres tears
- and eventually osteoarthritis of the hip.
FAI is a common condition, affecting 25% of people and is one of the most common causes of hip arthritis.
There are 2 types of FAI.
- CAM impingement. The bone abnormality is located on the ball.
- PINCER impingement. The bone abnormality is located on the socket.



