Femoroacetabular Impingement (Hip)

What Is Hip Impingement?

Femoroacetabular impingement occurs when the hip bones rub against each other excessively due to being an abnormal shape.

The hip is a ball-and-socket joint formed by:

Types of Hip Impingement

There are three main types of FAI hip depending on which bone is irregularly shaped:

1. Cam Impingement Hip: where the femoral head is not perfectly round, but more oval or flattened, which prevents it from rotating smoothly. A bump or “cam” develops on the edge of the femoral head which rubs against the articular cartilage causing damage. 
   
   
2. Pincer Hip Impingement: is caused by extra bone growth extending over the rim of the acetabulum, which can pinch the labrum between the bones during hip motion. 
   
   
3. Combined/Mixed Impingement: Some people present with both pincer and cam deformities, which intensifies symptoms and increases the risk of cartilage damage and labral tears

Cam impingement is the most common type of hip impingement, and typically causes symptoms in young men and athletes. Pincer hip impingement is more common in active middle-aged women.

What Causes Hip Impingement?

Several factors contribute to the development of femoroacetabular impingement:

• Abnormal shape may have been present since birth
• Abnormal bone development in the hip joint during adolescence
• Previous hip injuries or surgeries that alter joint shape
• Genetic predisposition to bone shape irregularities
• Structural issues like hip dysplasia or slipped capital femoral epiphysis that affect joint alignment
• Formation of bone spurs e.g. from hip osteoarthritis

In some cases, the abnormal bone shapes in hip impingement don’t cause any symptoms at all and people live active, pain free lives, often unaware they have femoroacetabular impingement.

However, in others the abnormal bony contact can lead to pain and stiffness. When hip impingement causes pain, it is known as Femoral Acetabular Impingement Syndrome (FAI Syndrome).

With FAI syndrome hip symptoms typically develop in active, sporty individuals whose activities involves lots of repetitive hip movements, especially twisting and squatting e.g. soccer, hockey, martial arts, or dance.

The repetitive movements place ongoing pressure and friction through the articular cartilage and labrum which can lead labral tears or cartilage damage.

Hip Impingement Symptoms

The signs of hip impingement syndrome can vary but typically include:

• Deep, aching pain in the groin or outer hip, especially after prolonged sitting or activity
• Hip stiffness and reduced range of motion
• Sharp pain with twisting, squatting, or pivoting movements
• Clicking, catching, or locking sensations in the hip joint
• Referred pain into the buttock or upper thigh

Femoroacetabular impingement symptoms tend to develop gradually, but in some cases, a specific incident may trigger sharp pain.

Femoral acetabular impingement syndrome can develop in the front or back of the hip:

1. Anterior Hip Impingement: at the front of the hip is more common and usually occurs during activities involving hip flexion, such as running or sitting.
2. Posterior Hip Impingement: at the back of the hip is less common but can cause pain during hip extension or external rotation.

Femoroacetabular impingement is a common cause of top of thigh pain.

Diagnosing FAI Hip Syndrome

Differential Diagnosis

Other conditions can mimic the signs of hip impingement syndrome and cause top of thigh pain such as:

• Hip labral tear
• Hip flexor strain
• Hip osteoarthritis
• Snapping hip syndrome
• Hip bursitis
• Lumbar disc herniation or nerve compression

Accurate diagnosis is essential to ensure the correct treatment for hip impingement syndrome.

How to Treat Hip Impingement

Femoroacetabular impingement treatment depends on the severity of symptoms and underlying structural problems, but can often be treated without surgery. Conservative hip impingement treatment usually involves:

• Activity Modification: Avoiding positions that aggravate symptoms, such as deep squats or prolonged sitting.
• NSAIDs: Non-Steroidal Anti-Inflammatory Drugs  e.g. ibuprofen or naproxen can help reduce inflammation and pain.
• Physiotherapy: Focused on improving hip strength, flexibility, and joint mechanics to offload stress on the impinged area.
• Corticosteroid Injections: Occasionally used to reduce inflammation and confirm the joint as the pain source.

Hip Impingement Exercises

A tailored rehab program for femoroacetabular impingement treatment should include:

• Core Stabilization: Exercises like planks and bird-dogs
• Hip Mobility: Dynamic stretches for hip impingement and controlled joint rotations
• Strengthening Exercises: Such as glute bridges, side-lying leg lifts, resistance band clamshells
• Neuromuscular Re-Education: To improve posture and reduce hip stress during daily activities

Exercise therapy is one of the most important aspects of non-surgical hip impingement treatment and can help delay or avoid surgery.

Hip Impingement Syndrome Surgery

When conservative management fails to alleviate symptoms or if structural damage is significant, surgery for femoroacetabular impingement may be necessary.

• Hip Arthroscopy: The most common type of hip impingement syndrome surgery, involving small incisions and a camera to guide instruments. Surgeons can:
  - Reshape the femoral head (cam lesion removal)
  - Trim back excessive acetabular rim (pincer lesion correction)
  - Repair or remove damaged labrum
  
  
• Open Surgery: Used in more complex cases or where joint preservation requires more extensive correction.

Hip Impingement Surgery Recovery Time

Around 70–90% of patients report significant pain relief and improved function after hip arthroscopy for FAI

Return to non-sporting activity is typically possible within 3–4 months

Athletes often resume sports within 4–6 months, depending on the extent of the repair and rehabilitation progress

Post-operative rehabilitation is crucial for optimal outcomes and reducing the risk of recurring hip impingement symptoms.

Femoroacetabular Impingement Summary

Femoroacetabular impingement (FAI) syndrome is a key cause of hip pain and movement limitation in active adults. Caused by bone shape abnormalities and aggravated by repetitive motion, hip impingement syndrome can lead to significant discomfort and eventual joint damage if not treated.

Diagnosis involves specific clinical tests and imaging, while treatment ranges from exercise-based therapy to surgery in more advanced cases. Early recognition and targeted hip impingement treatment can restore function, relieve pain, and help prevent long-term joint issues.

If you're dealing with persistent hip pain, don't ignore the symptoms—get assessed for FAI hip and take the first step toward recovery.

You may also be interested in the following articles

• Top Of Thigh Pain
• Pain Above The Knee
• Knee Clicking & Popping
• Hip Strengthening Exercises
• Knee Strengthening Exercises

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Last Updated: May 8th, 2025
Next Review Due: May 8th, 2027