Femoroacetabular Impingement (FAI)

What is it?

The hip is a ‘ball and socket’ joint which should move smoothly without causing joint damage. Femoroacetabular impingement (FAI) occurs when the bones of the hip are shaped abnormally and is the most common cause of hip pain in patients who visit the Fortius Clinic.


In many cases, FAI is caused by the ball of the ball and socket joint developing a slightly flattened shape during late childhood and adolescence. Where the deformed ball and socket don’t fit together perfectly, they rub against each other, causing joint damage at the front of the hip. FAI can also affect people without a deformity, but who take part in activities that put excessive stress on the hip joint, such as dance.

Athletes are more likely to experience pain as a result of FAI than others who have hip deformities, because the hip joint is worked much harder. It can be made worse by sports that involve running very fast, then pivoting on the affected hip. In many cases, these athletes may have previously had problems with their hamstrings or adductor muscles.

Problems can be made worse by the type of surface, with athletes who play on artificial grass more likely to be affected.

There are two main types of FAI, although in some cases you may be affected by both:

  • Pincer– where extra bone extends beyond the rim of the hip socket (acetabulum), putting pressure on the labrum (the rubbery rim of fibrous tissue surrounding the socket)
  • Cam– where the ‘ball’ section of the ball and socket hip joint (femoral head) isn’t perfectly round, so cannot move smoothly inside the socket (acetabulum); this can damage the labrum and cartilage at the front of the hip socket


Symptoms include:

  • Groin pain
  • Pain that is felt towards the outside of the hip, or in the buttock
  • Gradual reduction in the ability to exercise, particularly running, exercise classes and sports involving pivoting and twisting
  • Stabbing pain when twisting, turning, getting up from a chair or squatting – and a dull ache at other times
  • Pain after you have been sitting down for a long time, for example driving, or when sitting in a confined space such as at the cinema or on a plane

Once symptoms have begun to develop, it means there is already damage to the cartilage or labrum and this usually becomes gradually worse.


After a discussion of your symptoms and a medical examination, the specialist’s diagnosis can be backed up by X-rays, and CT scans to show the type of impingement, as well as any signs of permanent damage to the lining cartilage of the socket. You may also have an MRI scan to look for labral tears, damage to the cartilage or other associated soft tissue injuries.


Non-operative treatment: this may involve avoiding activities that make your symptoms worse, along with taking anti-inflammatory medication if advised by your doctor. At the Fortius Clinic, we will also design a targeted rehabilitation programme of exercises to increase the range of movement in your hip and strengthen your muscles to relieve pressure on the injured cartilage.

Surgery: if non-operative treatment doesn’t relieve your symptoms, you may be offered arthroscopic surgery to reshape the bone, repair the labrum and potentially stimulate repair of damaged cartilage.

Important: This information is only a guideline to help you understand your treatment and what to expect. Every person is different and your rehabilitation may be quicker or slower than other people’s. Please contact us for advice if you are worried about any aspect of your health or recovery.

Arthroscopy is a type of keyhole surgery used to diagnose and treat joint problems.
Hip replacement surgery is carried out when other treatments such as medication and changes in your activities and lifestyle have not relieved your symptoms.
This procedure involves changing the orientation of the hip socket in patients with hip dysplasia.

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