Understanding Femoral Acetabular Impingement (FAI): Key Causes and Symptoms Explained

Femoroacetabular impingement (FAI) is a condition that affects the hip joint, causing discomfort and limitations in certain movements. It occurs when the bones of the hip, specifically the Femur (thighbone) and the Acetabulum (part of the pelvis), are abnormally shaped, leading to friction between them during movement.

This rubbing can often cause pain, muscle guarding, swelling, and restricted activity. In addition, this can also take a toll on the mental side of things with frustration and anger.

The causes of FAI can be varied, including genetic predispositions to the development of extra bone along the hip bones. This abnormal bone growth, along with other risk factors such as physical activities or injuries, contributes to the occurrence of FAI.

Symptoms of this condition often include hip and groin pain, stiffness, and reduced range of motion, which can significantly impact a person’s daily life and activities.

In this blog post, we’ll go into greater detail on the causes and symptoms to help you understands if you have FAI and what the symptoms are to help you to be better educated and more capable of treating yourself along the way.

Key Takeaways

  • Femoroacetabular impingement (FAI) is caused by irregular hip joint bone structure, leading to friction and discomfort during movement.
  • Risk factors such as genetics, extra bone growth, and certain physical activities can contribute to the development of FAI.
  • Symptoms of FAI include hip and groin pain, stiffness, and decreased range of motion, impacting an individual’s quality of life.

Causes of Femoral Acetabular Impingement

Femoral Acetabular Impingement (FAI) occurs when the hip bones do not normally form during childhood growth, leading to altered joint mechanics, potential damage, and pain.

The main causes of FAI can be categorized into three subtypes: Cam Impingement, Pincer Impingement, and Combined Impingement.

Femoral Acetabular Impingement (FAI): Different types

Cam Impingement

Cam impingement is characterized by an aspherical or not perfectly round femoral head, leading to abnormal contact between the head and socket as the hip goes through a range of motion. Cam Impingements are more common in young male athletes.

The loss of roundness in the femoral head can be attributed to but always accompanying conditions such as slipped capital femoral epiphysis or Perthes disease. This type of FAI is more common in male athletes due to increased stress on the hip joint during sports activities.

Pincer Impingement

In Pincer Impingement, the cause is related to a deformity in the acetabulum or the hip socket. The acetabulum is too deep or has an extra bone, causing the femoral head to have limited space and impinge upon the rim of the socket. The Pincer type of FAI is more common in young female athletes.

This leads to pain and restricted hip movement. Pincer impingement is more prevalent in middle-aged women and may increase the risk of hip osteoarthritis development.

Combined Impingement

Combined impingement is the presence of Cam and Pincer deformities in the hip joint, resulting in abnormalities in the femoral head and the acetabulum. This type of FAI increases the susceptibility to joint issues and pain due to the simultaneous abnormal contact between the femoral head and the hip socket.

Patients with combined impingement may experience more severe symptoms and limitations in their hip movements and could be more likely to have surgery to fix.

Risk Factors and Prevalence


Femoral Acetabular Impingement (FAI) is commonly observed in athletes, particularly those involved in sports requiring forceful, repetitive hip movements or high impact on the joints. Research indicates that young adults, especially between the ages of 20 and 45, are more susceptible to FAI due to increased physical activity during this phase of life 1.

Athletes engaged in sports like soccer, football, tennis, baseball, and lacrosse are often more prone to FAI as these activities involve sudden changes in direction, quick pivots, and deep hip flexion 2. Golfers, rowers, and martial artists may also experience hip impingement due to the repetitive swinging, rowing, or kicking motions integral to these sports.

Through early diagnosis and activity modification, athletes may prevent the progression of FAI and alleviate hip pain associated with the condition.

It’s important to get athletes who participate in these sports on an early strength and conditioning program to create symmetrical strength patterns and hip stability at an early age.

One of the biggest mistakes we see is athletes who specialize in one sport year-round and don’t have a strength and conditioning program outside of their selected sport.


High-impact activities or those requiring repetitive hip motions are significant risk factors for the development of FAI. For instance, those participating in soccer and football face a higher risk of impingement as these sports involve extensive running, pivoting, and jumping 3.

The repetitive strain may contribute to hip joint irregularities in tennis and baseball, where players rely on explosive lateral movements and rotation. Golfers, rowers, and martial artists may also face an increased risk of FAI due to the aforementioned motions associated with their respective activities.

Think of sports with a lot of planting on the affected leg with forceful twisting.

Incorporating modifications in training practices, focusing on correct techniques, and identifying hip impingement symptoms early on could play a crucial role in managing the condition among athletes and active individuals.


  1. https://www.yalemedicine.org/conditions/femoroacetabular-impingement-syndrome
  2. https://orthoinfo.aaos.org/en/diseases–conditions/femoroacetabular-impingement/
  3. https://my.clevelandclinic.org/health/diseases/21158-femoroacetabular-impingement-fai

Symptoms and Identifying Pain

Groin Pain and Discomfort

Femoroacetabular impingement (FAI) often causes pain and discomfort in the groin area. This pain typically worsens after physical activities such as after sports or prolonged sitting, making everyday tasks more challenging for individuals with FAI.

Groin pain can also be accompanied by stiffness, which might restrict the range of motion in the hip joint, further limiting normal movement. The groin pain is usually easily reproduced by specific movements, such as hip flexion, and tends to occur at the same point in the motion each time.

Hip Joint referral pattern
Hip Pain Pattern and Referral Location

Buttock and Back Pain

In addition to groin pain, FAI can cause discomfort in the buttock and lower back regions. It may even start as a low deep ache in the posterior glute and back, which is easy to discount as other aches and pains.

It is crucial to be aware of any persistent pain in these areas, as they can also be indicative of FAI.

Clicking and Catching Sensations

People with FAI might experience clicking or catching sensations within the joint. These sensations may change how they move and cause discomfort, especially during activities requiring a wide range of motion.

A locking sensation may also occur, limiting movement and making it difficult to perform simple tasks like putting on socks or shoes. In some cases, these sensations could also lead to limping. This is key!

If a report of locking with an associated painful click doesn’t go away with rest, it’s time to get the hip looked at.

In conclusion, to identify potential FAI symptoms, paying close attention to any persistent pain in the groin area, buttock, or back, along with clicking, catching, or locking sensations within the joint, is crucial.

Diagnosis and Physical Examination

When diagnosing femoroacetabular impingement (FAI), the doctor begins with a detailed medical history and a physical examination of the patient. Particular emphasis is given to assessing the range of motion and identifying any pain points during the exam.

A common method used to identify hip impingement is the impingement test, where the doctor rotates the hip inwards with the hip and knee bent to check for pain or discomfort. This is called a Scour’s Test or a FADDIR test.

Imaging Tests

X-rays: After the physical examination, the doctor may order X-rays to visualize the hip joint better. X-rays provide detailed images of the bones and can help identify any unusual bone growth or irregularities in the hip joint that may be causing the impingement. This can be helpful for both Cam and Pincer deformities however will not show the condition of the labrum or any other soft tissue.

Radiograph of a Cam Impingement
X-ray of a Cam Impingement

Magnetic Resonance Imaging (MRI) scans: In some cases, the doctor might also request magnetic resonance imaging (MRI) scans. MRI scans provide a more detailed view of the joint, including the soft tissues such as the labrum and cartilage. This can help identify any damage to these structures that might be contributing to the pain and discomfort associated with FAI.

It is important to note that imaging tests alone may not provide a definitive diagnosis, as some individuals may have hip joint abnormalities without experiencing any symptoms. A combination of the patient’s medical history, physical examination, and imaging findings is crucial in determining the presence of femoroacetabular impingement.

Non-surgical Treatment Options

Rest and Activity Modification

One of the initial treatments for femoroacetabular impingement (FAI) involves incorporating some initial rest and activity modification for patients. During this stage, avoiding activities that can aggravate symptoms, such as sports or physical work that require excessive hip movement, is crucial.

Gradually, patients can reintroduce their regular activities on a case-by-case basis as symptoms subside to identify further the motions or activities that cause pain.

Complete rest is not recommended!

Soft tissue injuries do not respond to complete rest and need light loading to lay down new fibers and start the healing process.

Physical Therapy and Exercises

Another essential component of managing FAI is physical therapy. This non-surgical treatment aims to increase the range of motion, strength, and flexibility of the hip joint, helping to reduce pain and improve function.

Patients might work with a physical therapist who designs a tailored exercise program, focusing on specific muscle groups to stabilize and support the hip joint.

Exact exercises will be covered in more detail in a separate post; however, improving the strength and tissue tolerance of the hip muscles, tendons, and ligaments is absolutely critical.

Squats for hip strength
Squats for Glute and Hip Strength

Several exercises can help strengthen the hip muscles and improve mobility for individuals with FAI. Here are some of the best hip-strengthening exercises for FAI in the early phases:

  1. Clamshells: Lie on your side with your knees bent and feet together. Keeping your feet touching, lift your top knee as high as possible without moving your pelvis. Lower the knee back down and repeat for several reps.
  2. Side-lying leg lifts: Lie on your side with your bottom leg bent and your top leg straight. Lift the top leg as high as possible without moving your pelvis, then lower it back down. Repeat for several reps.
  3. Single-leg Hip bridges: Lie on your back with your knees bent and feet flat on the floor. Lift your hips up towards the ceiling, squeezing your glutes and hamstrings. Lower your hips back down and repeat for several reps.
  4. Single-leg squats: Stand on one leg with your other foot lifted. Slowly lower yourself into a squat, keeping your knee aligned with your toes. Return to standing and repeat for several reps before switching legs.
  5. Lunges: Stand with your feet hip-width apart and take a large step forward with one foot. Lower your body towards the floor, keeping your knee aligned with your toes. Push back up to standing and repeat for several reps before switching legs.

Medication and Pain Relief

To manage pain and inflammation associated with FAI, doctors often recommend the use of nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen or naproxen. These medications help relieve pain and decrease inflammation in the hip joint, allowing patients to participate in physical therapy more comfortably.

However, long-term use of NSAIDs is not recommended. We also want a small amount of inflammation to lay the building blocks for tissue repair. Our saying is to “take medication if you can strengthen without pain.”

In some cases, a healthcare professional might administer a local anesthetic or corticosteroid injection directly into the affected joint to provide temporary pain relief. This intervention might be especially beneficial for patients with severe pain or those who do not respond well to oral medications.

However, injections should be used judiciously, as they may cause potential side effects and are not suitable for long-term management of FAI.

In conclusion, non-surgical treatment options, such as rest and activity modification, physical therapy, and medications, play a crucial role in managing and alleviating symptoms associated with femoroacetabular impingement. These conservative treatments must be tailored to individual needs and should always be approached with a clear understanding of the potential risks and benefits involved.

Surgical Treatment Options


Arthroscopy is a minimally invasive surgical treatment for femoroacetabular impingement (FAI). This procedure involves the use of an arthroscope, a small camera, to view the hip joint and surrounding structures.

Surgeons make small incisions around the hip area and insert the arthroscope to identify and treat FAI-related damage1. Arthroscopy allows for a shorter recovery time and less postoperative pain compared to open surgery, as there is less damage to the soft tissue during surgery.

However, it may not be suitable for all cases, depending on the severity and location of the impingement.

Open Surgery

In some cases, open surgery may be necessary to treat FAI. This type of operation involves a larger incision and direct access to the hip joint for a more comprehensive view and treatment of the affected area2. Open surgery may be recommended when arthroscopy is not sufficient or when additional procedures, such as bone grafting or joint reconstruction, are needed.

While this approach typically requires a longer recovery period and potentially more discomfort, it can be essential for more complex and severe cases of FAI.


  1. Surgery for Femoroacetabular Impingement (FAI) – Stanford Health Care
  2. Femoroacetabular Impingement – OrthoInfo – AAOS

Frequently Asked Questions


  1. https://www.yalemedicine.org/conditions/femoroacetabular-impingement-syndrome 2
  2. https://stanfordhealthcare.org/medical-conditions/bones-joints-and-muscles/femoroacetabular-impingement/causes.html 2 3
  3. https://www.hopkinsmedicine.org/health/conditions-and-diseases/hip-impingement


Femoral Acetabular Impingement (FAI) is a condition that occurs when the hip joint is not properly shaped, causing the bones to rub against each other, leading to pain and limited motion. It primarily affects individuals between the ages of 20 and 45, making it a common cause of hip and groin pain in this age group.

The exact cause of FAI is often unknown, but it is associated with abnormalities in the development of hip bones during childhood. Joint damage and pain occur with the deformity of either a cam bone spur, a pincer bone spur, or both.

Diagnosis of FAI involves a comprehensive evaluation, including a physical exam, X-rays, and potentially an MRI scan. Treatment options vary depending on the severity of the condition and may include conservative measures such as physical therapy and pain management, as well as surgical intervention for more severe cases.

In summary, understanding Femoral Acetabular Impingement is crucial for identifying and addressing the cause of hip pain and limited mobility in affected individuals. Being knowledgeable about its causes and symptoms helps clinicians provide accurate diagnoses and tailored treatment plans to alleviate pain and improve patient’s quality of life.

2 thoughts on “Understanding Femoral Acetabular Impingement (FAI): Key Causes and Symptoms Explained”

  1. Pingback: The 7 Best Stretches for Femoral Acetabular Impingement: Top Techniques to Ease FAI

  2. Pingback: The 6 Best Strengthening Exercises for Hip FAI: A Friendly Guide to Pain-Free Hips - The Hip PT

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