What is Femoroacetabular impingement syndrome?

Femoroacetabular impingement (FAI) syndrome is a movement-related problem of the hip, often leading to pain in the hip or groin region. It is caused by abnormal or premature contact between the top of the thigh bone and the hip socket during movement, or in certain positions. 

For the syndrome to be properly diagnosed, three main criteria are required:

  • A patient must report symptoms, such as hip or groin region pain, clicking, catching, or giving way
  • Certain clinical signs must be present, for instance, reduced range of motion of the hip 
  • Certain ‘features’ must be seen on x-ray of the hip: usually a ‘cam’ or ‘pincer’ lesion

hip cam

Anatomy of femoroacetabular impingement syndrome:

The hip is a ball and socket joint. The socket is called the acetabulum and is part of the pelvis. The ball is at the very top of the femur (thigh bone) and is called the ‘head of the femur.’ 

In FAI syndrome, one or two features are seen on x-ray:

  • A ‘cam’ shape: a ‘bump’ of bone may be seen at the junction of the ‘head’ and the ‘neck’ of the femur bone, causing an area of convexity
  • A ‘pincer’ shape: the acetabulum (socket) has too much coverage or overhang over the top of femur
  • A mix of the two features above 

These bone features can be responsible for reducing the amount of ‘clearance’ within the hip joint, causing abnormal contact to occur between femur and the socket. Over time, this contact may lead to inflammation within the hip (synovitis), as well as potential damage to the cartilage within the joint, particularly the labrum, which is a ring of fibrocartilage that lines the rim of the socket. 

What are the symptoms of femoroacetabular impingement syndrome? 

The primary symptom of FAI syndrome is movement related, or positional related pain in the hip or groin region. However, pain may also be felt in the lower back, buttock or thigh. In addition to pain, patients may also describe stiffness, clicking, catching, locking or giving way. 

These symptoms are often felt either during or after vigorous physical activity, such as sports including AFL and soccer, or sports that require a lot of range of movement of the hip, such as dance, gymnastics and calisthenics. However, since symptoms can be related to certain positions of the hip, those who live more sedentary lifestyles can also experience symptoms, for example, when sitting for too long. 

Do I have femoroacetabular impingement syndrome?

Just having the features of FAI on x-ray, such as a ‘cam’ or ‘pincer’ lesion does not mean that you have FAI syndrome. 

For the syndrome to be present, you must also be experiencing the symptoms of FAI as mentioned above, as well as the ‘clinical signs’ present when your hip is examined by a doctor or physiotherapist, such as reduced range of motion, or pain that is provoked with certain clinical tests.

Other tests such as MRI or CT scan may be required, especially if any surgery is planned. Sometimes, a local anaesthetic injection may be used in the hip may be used to help determine whether your symptoms are arising from within the hip, or from many of the other structures around the hip. 

Treatment of femoroacetabular impingement syndrome:

FAI syndrome can be treated by conservative care, rehabilitation or surgery.

Conservative care involves education, monitoring of symptoms over time and lifestyle and activity modification. 

Physiotherapy based rehabilitation aims to improve hip stability, hip muscle strength, range of motion and movement patterns.

Surgery, which is usually performed arthroscopically (keyhole), aims to improve the hip joint shape (morphology) and repair any damaged tissue in the hip, such as the labrum (cartilage).

A recently published, large clinical trial in the UK (The ‘FASHIoN Study’), showed positive outcomes from both physiotherapy-led and surgical treatment options for FAI syndrome. 

Without treatment, symptoms of FAI syndrome will probably worsen over time. The long-term outlook for patients with FAI syndrome is unknown. However, it is likely that having a cam shape is associated with the development of hip osteoarthritis

Differential diagnosis: 

It is important a proper diagnosis is performed, as FAI syndrome must be differentiated from other conditions that may cause hip and groin pain, such as:

  • Hip joint instability or hip joint dysplasia (eg. a ‘shallow’ hip socket)
  • Gluteal (buttock muscle) tendon problems
  • Adductor (groin muscle) tendon problems
  • Iliopsoas (hip flexor muscle) tendon problems
  • Inguinal hernia 
5 tips for self-managing FAI syndrome: 
  1. Avoid sitting in cross-legged positions (especially where one knee is crossed over the other)
  2. Avoid sitting in positions where the hips are positioned ‘lower’ than the knees, for example, sitting on a low couch. Always try to have your hips higher than the knees.
  3.  When performing stretching exercises for the back and leg muscles, always ensure that you are feeling a good stretch in the desired muscle. If you experience deep hip or groin region pain when stretching, rather than a muscle stretch, this may be counter-productive.
  4. Avoid excessively deep squats and lunging-type movements.
  5. If you are a side sleeper, try sleeping with a pillow between your knees to ensure your thigh does not cross over the other during the night 
Return to activity:

In patients who are treated for FAI syndrome, symptoms frequently improve, and they return to full activity, including sports.


The Warwick Agreement on femoroacetabular impingement syndrome (FAI syndrome): an international consensus statement. Griffin DR, et al. Br J Sports Med 2016;50:1169–1176.

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Hip Physiotherapists

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