Hip Impingement (FAI)

Name: Hip Impingement (Femoroacetabular Impingement)
Creator: Prof Paul Lee

Femoroacetabular impingement occurs when abnormal bone shape at the hip creates friction during movement, damaging the labrum and cartilage. Early recognition and treatment can prevent progressive joint damage.

Reviewed byProf Paul Lee MBBch, FRCS (Tr & Orth), PhDLast reviewed 1 May 2026

What causes hip impingement?

FAI is caused by abnormal bone morphology that develops during growth. The bone shape creates mechanical conflict between the femur and the socket during everyday hip movements, particularly flexion and rotation.

Cam morphology: a bony prominence on the femoral head-neck junction.
Pincer morphology: over-coverage of the femoral head by the socket rim.
Mixed: combination of both, present in the majority of symptomatic patients.

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Symptoms and diagnosis

FAI typically presents with:

Groin pain that worsens with sitting, squatting, or pivoting movements.
Stiffness and loss of hip rotation, particularly internal rotation.
Sharp pain at end-range hip flexion (the “C-sign” where patients cup the front of the hip).
Pain during or after sport, particularly activities involving deep hip positions.

Diagnosis is confirmed with plain X-rays to assess bone morphology and MRI arthrogram to evaluate the labrum and cartilage.

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Treatment at London Cartilage Clinic

Treatment is tailored to the severity of impingement and the degree of soft tissue damage. Our hip specialists offer both conservative and surgical pathways.

For patients with progressive labral damage or cartilage wear, hip arthroscopy to reshape the bone and repair the labrum addresses both the cause and the consequence of impingement. The goal is to restore pain-free hip movement and protect the joint from further degeneration.

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You may have more options than you think

Most patients have more treatment options than they have been told

At London Cartilage Clinic we follow a structured clinical framework across four areas of treatment. Before recommending a single procedure, we assess which combination of approaches gives you the best outcome.

Preserve

Protect what you have. Slow degeneration and manage symptoms.

Repair

Fix specific damage. Torn tissue, unstable joints, structural problems.

Regenerate

Rebuild lost tissue. Biological treatments that stimulate new growth.

Replace

When other options are exhausted. Joint replacement as a last resort.

Explore the full range of treatments available for your joint. Each hub page shows every option we offer, organised by clinical approach.

Explore Hip Options

Frequently Asked Questions

What is femoroacetabular impingement?

FAI is a condition where abnormal bone shape at the hip joint causes the femur (thigh bone) and acetabulum (socket) to make contact during normal movement. This repeated friction damages the labrum and cartilage over time, leading to pain and potentially early arthritis.

What is the difference between cam and pincer impingement?

Cam impingement involves a bump on the femoral head that jams into the socket during flexion. Pincer impingement involves excess bone on the socket rim that grips the femoral neck. Many patients have a combination of both, known as mixed impingement.

Does FAI always need surgery?

Not always. Mild FAI with manageable symptoms may respond to physiotherapy and activity modification. However, if the impingement is causing progressive labral or cartilage damage, arthroscopic surgery to reshape the bone and repair the labrum may be recommended to protect the joint long-term.

What does FAI surgery involve?

Hip arthroscopy is used to reshape the abnormal bone (osteoplasty) and repair the damaged labrum. The procedure addresses both the cause (bone shape) and the consequence (soft tissue damage) in a single operation.

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