What is femoroacetabular hip impingement?

FAI (femoroacetabular hip impingement) can happen for a variety of reasons, and it’s often a combination of them that leads to the diagnosis. A change in the bony structure and/or a labral tear of the hip joint are the most common causes of FAI. Femoroacetabular hip impingement can be caused by two types of anatomical variations:

  • An overabundance of bone on the femoral head/neck is known as a cam lesion.
  • An overabundance of bone on the acetabulum of the pelvis is known as a pincer lesion.

When one or both of these lesions are present, the hip joint structures can be pinched or impinged (mainly the cartilage around the edge of the joint). This impingement of the hip joint can produce pain over time, especially when sitting for lengthy periods of time or exercising. A labral tear is a common symptom of femoroacetabular hip impingement. The labrum is a cartilage layer that surrounds the socket of the hip joint. When repeated impingement occurs, it is vulnerable to harm.

What are the symptoms of femoroacetabular hip impingement?


The following are common signs of femoroacetabular hip impingement:

  • A profound pain in the front of the hip/groin that can spread to the outside of the hip and even the buttocks. This can be either a sharp or a dull aching.
  • Prolonged sitting, standing after sitting, walking, and exercise, particularly twisting and turning sports like football, enhance pain.
  • A overall sensation of hip stiffness.
  • A sensation of weakness in the hip.

With femoroacetabular hip impingement, patients may experience clicking and a sense of giving way.

What other conditions can present like Femoroacetabular hip impingement? 

  • Greater trochanteric pain syndrome
  • Hip osteoarthritis
  • Osteitis pubis
  • Iliopsoas tendinopathy/bursitis
  • Proximal hamstring tendinopathy

If this sounds like your pain, read on…

 Femoroacetabular hip impingement vs hip osteoarthritis:

A femoroacetabular hip impingement is a type of joint impingement. It most typically affects young persons between the ages of 20 and 40, and is generally linked with poor hip muscle control, stiffness, and sub-optimal movements while walking, jogging, or participating in sports.
Hip osteoarthritis is another joint-related disease. Osteoarthritis is a gradual, degenerative disorder in which the joint’s cartilage layer (which offers friction-free movement) is degraded. Osteoarthritis is a painful disorder that causes stiffness in the joints. This is most frequent in adults over the age of 50, and it usually gets worse as they get older.
The front of the hip and the groyne are affected by both femoroacetabular hip impingement and osteoarthritis of the hip. In addition, these disorders cause hip stiffness in the morning. Both illnesses can be quite painful, especially while performing hip flexion exercises, however femoroacetabular hip impingement is more common in younger people than hip osteoarthritis.

Anatomy of the hip:

The articulation of the huge ball-shaped head of the femur (long bone of the thigh) and the cup-shaped socket of the pelvis forms the hip joint (called the acetabulum).

The labrum, a fibrocartilage ring that surrounds the acetabulum, supports this huge load-bearing joint. By enlarging the acetabulum’s socket, the labrum improves joint stability. The hip joint is covered in articular cartilage and bathed in synovial fluid, which reduces friction.

What is femoroacetabular hip impingement (FAI)?

Femoral acetabular hip impingement can be caused by minor anatomical differences in the hip’s bony structure. When these differences exist, the acetabulum and the femoral head and neck may come into contact, causing pain and impingement (Hendry et al., 2013).

With femoral acetabular hip impingement, there are two major structural (bony) alterations. The following are some of them:

  • Cam lesions are defined as an overabundance of bone on the head or neck of the femur. This surplus of bone can collide with the acetabulum as the hip moves, causing a bony pinch or ‘impingement.’
  • Pincer lesions are characterised by an overabundance of bone on the acetabulum’s rim. As the hip moves, this bony protuberance hooks on the femoral head/neck, injuring the femur directly. Due to a lever-action generated by the pincer lesion, hip joint pathology can also emerge on the opposite side of the joint.
  • It’s not unusual for patients to have both Cam and Pincer lesions at the same time (Cheatham et al., 2016).

Femoral acetabular impingement is a prevalent source of hip discomfort in both young and middle-aged people, and it’s been linked to secondary hip osteoarthritis (Park et al., 2012).

Osteoarthritis most typically affects weight-bearing joints including the hip and knee [cornerstone hip article]. According to recent studies, articular cartilage requires adequate quality joint mobility to stay healthy. The articular cartilage might become thinner and weakened as a result of improper movement patterns or persistent inadequate stress (Clarke et al., 2003). Osteoarthritis is a degenerative condition caused by this process.

Fortunately, studies has shown that keeping adequate joint flexibility and strength might help delay the disease development linked with osteoarthritis (Hunter et al, 2009).

According to Cheatham et al., (2016), femoral acetabular impingement is primarily congenital. However, femoral acetabular impingement is linked to a number of risk factors (FAI). These are some of them:

  • Hypomobility of the hip joint (reduced range of motion)
  • Muscle stiffness and tightness in the hip musculature
  • Gait pattern that isn’t quite right (differences in the way you walk have been observed in patients with FAI)
  • Patients with FAI frequently experience hip muscle weakness (46 percent of FAI patients have been shown to exhibit weakness in the lateral gluteal muscles, used to stabilise the hip joint)
  • Patients with FAI have also been seen to have changes in their pelvic posture.
  • After a hip fracture, the risk of FAI increases.

According to research published by Hendry et al (2013) and Cheatham et al (2016), common symptoms related with FAI include:

FAI symptoms and signs:

  • The discomfort in the anterior (front) of the groin might be described as sharp or as a deep agonising sensation.
  • Pain can also radiate from the outside of the hip and into the buttocks.
  • A feeling of stiffness or a limited range of motion in the hip
  • When addressing the site of symptoms, patients frequently cup their palm around the front and side of the hip. The ‘C sign,’ as it is known, is a symptom of hip joint disease (see above image)
  • Pain that gets worse when you sit, stand, or move for long periods of time (research is showed this to be present in over 96 percent of FAI patients)
  • Hip pain is most common when performing exercises that require hip flexion, adduction, and internal rotation, such as crossing legs or performing hip stretches like the ones shown below.
  • Pain when participating in sports that require the hip to rotate or pivot, such as football.
  • When suffering from FAI, many patients experience clicking and a sense of giving way.
  • Many patients with FAI have been shown to have hip muscle weakness. As a result of the loss of control of the joint during movement, symptoms may develop.

How do we diagnose FAI?

An correct diagnosis of FAI must be made as soon as possible to ensure that the treatment you get is effective.

It is fairly uncommon for FAI to be misdiagnosed, as many illnesses can present in a similar manner. If you believe you may be suffering from this problem, you should get professional advice from one of our physiotherapists.

There are a number of different disorders that can mimic femoral acetabular impingement and must be ruled out before a diagnosis of FAI can be made. These are some of them:

  • Osteoarthritis of the hip
  • Tears in the labrum
  • Psoas tendonitis and bursitis
  • Lower back pain caused by a disc
  • Hernia in the groin
  • A thorough clinical examination and diagnostic imaging are required for an accurate diagnosis. These will be discussed further down:

An examination in the clinic:

A clinical examination is done to provide information to the physiotherapist about the variables that have contributed to the onset of your symptoms. It’s utilised to come up with a hypothesis for why you’re in pain and to come up with a therapy plan to address these concerns.

To further comprehend your circumstances, a clinical interview is conducted. Questions will be asked about how and why your pain began, what aggravates and relieves your symptoms, and how long you’ve been in pain. A complete medical history will be gathered as well.

Following that, a physical examination is carried out, which includes hip joint range of motion testing, strength and flexibility of the surrounding muscles, and palpation (feeling) of various hip structures. Squatting, single leg balancing, gait analysis, and running analysis are among the functional tests that are routinely conducted (if you are a runner).

This procedure can detect femoral acetabular impingement and provides a plethora of information about what’s causing your problems. However, imaging is essential to ascertain why you have this problem, such as whether you have a cam and/or pincer or a labral tear (cartilage tear around the hip socket).

Diagnostic Imaging:

The presence of femoral acetabular impingement must be confirmed through diagnostic imaging (Cheatham et al., 2016).


If your clinician suspects femoral acetabular impingement you may be referred for an initial x-ray. This is commonly used to assess bone and joint structure and is capable of assessing the shape of the bones of the hip joint as well as the quality of the joint space and presence of degenerative change.
Magnetic Resonance Imaging (MRI)

Both bone and soft tissue diseases can be accurately assessed with MRI imaging. MRI has been found to be the gold standard diagnostic technique for determining femoral acetabular impingement in studies. An MRI is a procedure that involves you laying immobile in a metal cylinder for 30 minutes to an hour. An MRI creates a detailed 3D representation of your hip architecture by taking a sequence of images of your hip.

Ultrasound imaging for diagnostic purposes

The outside edge of the hip joint, as well as the inflammation associated with femoral acetabular impingement, can be seen with diagnostic ultrasound imaging. It also has the added benefit of allowing you to visualise your hip while moving, which is useful for gauging pain during particular exercises.

Due to the depth of the hip joint, diagnostic musculoskeletal ultrasound imaging is not able to properly test for hip joint disease; nonetheless, it is a good imaging technique for assessing soft tissue hip pathology (Cheatham et al., 2016).

Joint Injections offers a staff of clinicians who are both physiotherapists and musculoskeletal sonographers with extensive experience. Your clinician will utilise both clinical examination and diagnostic imaging to assist evaluate the source of your hip discomfort during your evaluation.

How do we treat Femoroacetabular Hip Impingement Syndrome?

Due to the depth of the hip joint, most individuals with FAI are unable to adequately test for hip joint disease. It is, nevertheless, an useful imaging tool for determining the presence of soft tissue hip disease (Cheatham et al., 2016). Physiotherapy for femoral acetabular impingement usually works well.

  • Stretching and strengthening exercises for the hip muscles are part of a customised, progressive rehabilitation programme.
  • Advice on how to modify your activities to reduce the likelihood of aggravating your symptoms.
  • Re-education of movement — this could entail examining and adjusting how to properly squat or lunge.
  • Soft tissue release techniques can also help to relieve discomfort and improve hip flexibility.

    Here are a few pointers you might want to try:

  • Avoid exacerbating your symptoms by sitting for long periods of time and crossing your legs, which can irritate a hip with femoral acetabular impingement. If at all possible, stay away from these. If you’re a runner, this could mean cutting back on your running. 
  • You may need to take a break from running for a short time, and substituting non-weight bearing workouts like cross training will help. Stretch your hip muscles, especially the hip flexors, gently (see below)
  • The bridge, for example, is a Pilates exercise that can help you strengthen your hip muscles (see below image).

What if conservative treatment for femoral acetabular impingement doesn’t work?

An ultrasound-guided injection may be helpful for you if physiotherapy has been ineffective in lowering pain and symptoms and the diagnosis has been confirmed on imaging.

Patients who respond exceptionally effectively to corticosteroid injections typically report pain that:

  • wakes you up at night and interferes with your ability to sleep
  • is interfering with your ability to conduct daily chores, such as work and leisure activities.
  • has an impact on your ability to participate in physiotherapy rehab

Corticosteroid injection guided by ultrasound

For prolonged discomfort associated with femoral acetabular impingement, ultrasound-guided corticosteroid injection is a highly effective evidence-based therapy option (Park et al., 2013). A needle is precisely positioned within the hip joint during an ultrasound-guided injection. A modest amount of corticosteroid (a powerful anti-inflammatory drug often used in musculoskeletal injection therapy) is mixed with a short-acting local anaesthetic. An ultrasound-guided injection should provide pain relief for at least three months.

As a stand-alone treatment, injection therapy should be avoided. An ultrasound-guided injection creates a pain-free ‘window of opportunity’ for you to effectively rehabilitate your hip. Joint Injections recommend that a course of physiotherapy for FAI begin within two weeks following injection to obtain the best possible results.

Our clinicians are all fully qualified Extended Scope Physiotherapists (ESP), musculoskeletal sonographers, and independent prescribers at Joint Injections. For all ultrasound-guided injections, we may give same-day service.

Joint Injection’s experts are dual-trained, highly specialised physiotherapists and musculoskeletal sonographers with extensive experience diagnosing all hip and pelvis  disorders. We provide a ‘one-stop’ clinic, which means you’ll get an examination, a diagnostic ultrasound, and, if necessary, an ultrasound-guided injection.