Femoroacetabular Impingement (FAI)

Femoroacetabular Impingement (FAI)

Article by J.Miller, Z.Russell


What is Femoroacetabular Impingement?

Femoroacetabular Impingement (FAI) is a hip condition that describes a mechanical mismatch between the hip “ball” and the “socket”.

What Causes Femoroacetabular Impingement?

It is believed that many ordinary people have ‘bumps’ or slightly over-deep acetabular sockets (coxa profunda) and could potentially develop femoroacetabular impingement – this is just the way we are built and evolve.

The result of these deformities is increased friction between the acetabular socket and femoral head, resulting in pain and a decreased range of motion.

However, the hip has also to be provoked in some way to cause damage. This explains the tendency for athletes, sporting professionals and active people to be more susceptible to this form of injury.

How is Femoroacetabular Impingement Diagnosed?

The presence makes FAIS diagnosis is a combination of:

  1. Symptoms
  2. Clinical Signs
  3. Imaging Findings.

What are the Symptoms of FAI?

  • Hip or groin and buttock pain that is related to movement.
    • Pain is primarily felt deep in the groin at the front of the hip; more rarely, it can be on the side of the hip or the buttock.
  • Symptom onset can be acute, following injury, or insidious after prolonged exertion.  
  • Pain is often provoked with prolonged sitting, walking, crossing the legs, and during and after sport and exercise.  
  • There will typically be a restriction in hip flexion and internal rotation range of motion. 

What are the FAI Clinical Signs?

Physical examination involves a series of tests:

  • Symptom reproduction on the FAIR impingement test – hip flexion adduction and internal rotation;
  • When testing the hip range of motion, there may be a restriction in hip flexion and internal rotation;  
  • A weakness of your hip musculature;
  • Provocation of pain by flexion abduction and external rotation (FABER test) may provoke pain but is generally non-specific. 

Radiology Tests for FAI

Radiology investigations may confirm the diagnosis, with AP X-rays of the pelvis and lateral X-rays of the hips being the first line of inquiry. You may use subsequent imaging techniques such as a CT or MRI scan to clarify the status of the hip further and exclude any differential diagnosis conditions.

There are three described types of femoroacetabular impingement:

Cam Impingement

‘Cam’ type impingement describes a ‘bump’ on the surface of the femoral head (ball) which jams on the rim of the (acetabulum) socket. Cam typically affects young athletic men.

femoroacetabular impingement

Pincer Impingement

‘Pincer’ type impingement describes an increased coverage by the acetabulum over the anterior femoral head. Pincer impingement typically affects middle-aged women and is less common.


Mixed Type FAI

Often there can be a ‘mixed’ or combination of both cam and pincer types.

Cam Impingement

The result of these deformities is increased friction between the acetabular socket and femoral head, resulting in pain and decreased range of motion.

What Causes FAI?

FAI can be due to primary and secondary causes:

Primary or idiopathic causes are related to the activities we perform throughout our lifespan, and our body responds through our development, particularly in our youth years. This history explains the tendency for athletes, sporting professionals and active people to be more susceptible to this form of injury.

Secondary causes are often related to previous hip pathology or trauma, such as:

For specific advice regarding your hip or groin symptoms, please consult your hip physiotherapist or hip surgeon.

Femoroacetabular Impingement Treatment

Kemp et al. (2020) recommend that an initial treatment regime of non-surgical management of at least three months is advocated for most patients. Physiotherapy can assist by using a variety of techniques to:

  • mobilise the hip joint that stretches any tight structures 
  • improve soft tissue flexibility and length
  • strengthen the deep, intermediate and superficial hip muscles
  • progress hip muscle, proprioception, joint position sense and functional control to dynamically control your hip

The use of painkillers and anti-inflammatories may temporarily help the pain reduce the local anti-inflammatory reaction.

Hip Surgery for Femoroacetabular Impingement?

If your symptoms continue, despite non – surgical management, your Physiotherapist may discuss referral to an orthopaedic surgeon.

Post-FAI Hip Surgery Rehabilitation

A supervised rehabilitation program with a physiotherapist is an essential part of your post-surgical recovery.  Recovery from hip arthroscopy typically takes 3 – 4 months, while open hip debridement generally is 12 months.   

For more advice, please ask your hip physiotherapist or hip surgeon.

For a thorough assessment and the quickest relief from your groin pain, please contact your physiotherapist.

Acute Injury Signs

Acute Injury Management.

Here are some warning signs that you have an injury. While some injuries are immediately evident, others can creep up slowly and progressively get worse. If you don't pay attention to both types of injuries, chronic problems can develop.

For detailed information on specific injuries, check out the injury by body part section.

Don't Ignore these Injury Warning Signs

Joint Pain

Joint pain, particularly in the knee, ankle, elbow, and wrist joints, should never be ignored. Because these joints are not covered by muscle, pain here is rarely of muscular origin. Joint pain that lasts more than 48 hours requires a professional diagnosis.


If you can elicit pain at a specific point in a bone, muscle, or joint, you may have a significant injury by pressing your finger into it. If the same spot on the other side of the body does not produce the same pain, you should probably see your health professional.  


Nearly all sports or musculoskeletal injuries cause swelling. Swelling is usually quite obvious and can be seen, but occasionally you may feel as though something is swollen or "full" even though it looks normal. Swelling usually goes along with pain, redness and heat.

Reduced Range of Motion

If the swelling isn't obvious, you can usually find it by checking for a reduced range of motion in a joint. If there is significant swelling within a joint, you will lose range of motion. Compare one side of the body with the other to identify major differences. If there are any, you probably have an injury that needs attention.


Compare sides for weakness by performing the same task. One way to tell is to lift the same weight with the right and left sides and look at the result. Or try to place body weight on one leg and then the other. A difference in your ability to support your weight is another suggestion of an injury that requires attention.

Immediate Injury Treatment: Step-by-Step Guidelines

  • Stop the activity immediately.
  • Wrap the injured part in a compression bandage.
  • Apply ice to the injured part (use a bag of crushed ice or a bag of frozen vegetables).
  • Elevate the injured part to reduce swelling.
  • Consult your health practitioner for a proper diagnosis of any serious injury.
  • Rehabilitate your injury under professional guidance.
  • Seek a second opinion if you are not improving.