Femoro Acetabular Impingement (FAI), often referred to as Hip Impingement, is a mechanical disorder of the hip. It has become recognised more recently as a cause of hip pain and stiffness and can lead to hip arthritis.
Often in the early stages it is not painful and so can be undiagnosed for years. The diagnosis itself is made by taking a patient history, physical examination and imaging studies including x-rays and MRI scans.
There are two types of hip impingement, 'Cam' and 'Pincer' and you can get a combination of both. Normally the hip glides and moves smoothly as the ball shaped head of the femur moves in the cup shaped socket of acetabulum.
Cam Impingement is caused by a jamming or squeezing of an abnormally shaped femoral head and head-neck junction into the acetabulum during certain hip movements.
Pincer Impingement occurs when there is direct contact with the femoral neck or head-neck junction with part of the acetabulum edge and labrum. The acetabulum appears to be 'over deep.'
Treatment obviously depends on what form of impingement is present and is tailored to each individual. It can involve reshaping the femoral head and head-neck junction and/or recessing the acetabular rim and labrum.
When conservative methods of treatment fail to provide symptomatic relief then hip replacement surgery may be offered.