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Health condition · Clinically reviewed

Femoroacetabular impingement, the shape-based cause of hip pain in active adults.

A common source of groin pain in young adults and a recognised risk factor for early hip osteoarthritis. Modern hip preservation offers a clear stepped pathway from physiotherapy to keyhole surgery.

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A radiographer guides a patient onto the bed of an advanced 3 Tesla MRI scanner in a London imaging suite

Why trust this guide

  • 01

    Clinically reviewed

    Written by our editorial team and reviewed by a UK-registered clinician with hip preservation experience before publication.

  • 02

    Sourced from guidance

    Checked against BOA, BHS, NICE and peer-reviewed hip preservation literature listed at the end.

  • 03

    Current for 2026

    Reflects modern UK practice including hip arthroscopy for FAI, labral repair and the FASHIoN trial evidence base.

Key facts

FAI at a glance.

The essentials, in plain English - what FAI is, the three patterns and how it is treated in UK hip preservation today.

  • What it is

    A shape-based mismatch of the hip joint that pinches at end range and, over time, tears the labrum and damages cartilage.

  • Cam impingement

    A non-spherical femoral head-neck junction (asphericity) - most common in young men and athletes in cutting or pivoting sports.

  • Pincer impingement

    Over-coverage of the socket (deep or retroverted acetabulum) - more common in women in mid-life.

  • Combined pattern

    Around 85% of symptomatic FAI shows both cam and pincer features on imaging.

  • Why it matters

    FAI is a recognised risk factor for premature hip osteoarthritis - early diagnosis protects the joint.

  • Treatment

    Physiotherapy and activity change first; hip arthroscopy for symptomatic patients who fail conservative care (see /treatments/hip-arthroscopy-fai/).

Why this guide matters

A stepped hip preservation plan.

FAI is treatable and, in the right hands, joint-preserving. The three points below shape everything else on this page.

  • Diagnosis is clinical and imaged

    Groin pain plus a positive FADIR test and shape changes on a good AP pelvis and Dunn view - not just an MRI report.

  • Physiotherapy first

    A structured hip preservation rehabilitation programme resolves symptoms in a significant proportion of patients.

  • Surgery when it is warranted

    Hip arthroscopy in a designated centre outperforms conservative care for symptomatic FAI syndrome (FASHIoN trial).

How the diagnosis is made

From first groin pain to a clear hip plan.

The steps a UK GP, sports physician or hip preservation surgeon will normally follow, in order.

  1. 01

    Assessing

    History and sports profile

    Groin pain, activity triggers, sitting tolerance, driving and cutting or pivoting sports (football, ice hockey, dance).

  2. 02

    Assessing

    Clinical examination

    FADIR test (flexion, adduction, internal rotation), FABER, hip range, gait and Trendelenburg sign.

  3. 03

    Assessing

    Rule out mimics

    Groin, adductor and hip flexor pathology, sports hernia, greater trochanteric pain syndrome and lumbar referral.

  4. 04

    Confirming

    Plain radiographs

    AP pelvis, Dunn view and false profile - alpha angle, lateral centre-edge angle, crossover and ischial spine signs.

  5. 05

    Confirming

    MRI arthrogram

    Gadolinium MRI arthrogram is the reference test for labral tears and chondral damage (see /treatments/hip-mri-arthrogram/).

  6. 06

    Planning

    Diagnostic injection

    An image-guided intra-articular local anaesthetic and steroid injection can confirm the joint as the pain source.

  7. 07

    Planning

    Specialist hip preservation opinion

    Referral to a young-adult hip surgeon in a designated centre if symptoms persist or surgery is being considered.

Typical timeline: a first visit to a settled plan in weeks, not months.

Symptoms

What FAI actually feels like.

The classic mix of groin pain, positional symptoms and mechanical signs - and the features that mean it is time to escalate.

  • Anterior groin pain

    Deep, activity-related pain in the front of the hip or groin - the classic FAI symptom (see /conditions/groin-pain/).

  • Positional pain

    Worse with hip flexion, rotation, squatting, running, prolonged sitting and long drives.

  • Mechanical symptoms

    Clicking, catching or locking often signal an associated labral tear.

  • Reduced internal rotation

    Loss of internal rotation and flexion on examination, sometimes with a hard end feel.

  • Positive FADIR test

    Reproducing groin pain in flexion, adduction and internal rotation is the most sensitive clinical sign.

  • Labral tears

    Anterior-superior tears are the commonest structural consequence of FAI and drive many mechanical symptoms.

  • Cartilage damage

    Chondral delamination at the acetabular rim is the pathway from FAI to premature osteoarthritis.

  • Red flag - sudden severe pain

    Sudden severe hip pain with inability to weight-bear, fever or trauma needs urgent orthopaedic assessment.

Treatment

How FAI is treated in the UK.

Conservative care first, image-guided injection where useful, and hip arthroscopy in a designated centre for symptomatic disease.

  • Activity modification

    Reduce provocative loading (deep squatting, prolonged sitting, high-impact pivoting) while symptoms settle - short-term, not lifelong avoidance.

  • Specialist hip physiotherapy

    Gluteal and deep core strengthening, hip flexor and iliopsoas balance and neuromuscular retraining under a hip-preservation-trained physiotherapist.

  • NSAIDs and analgesia

    Short courses of oral or topical NSAIDs and simple analgesia to allow rehabilitation - not a long-term strategy.

  • Intra-articular steroid injection

    Ultrasound or fluoroscopy-guided joint injection - both diagnostic and therapeutic (see /treatments/cortisone-injection-large-joint/).

  • PRP or hyaluronic acid

    Selective use in labral or chondral pathology - evidence is evolving and best guided by a hip specialist.

  • Hip arthroscopy for FAI

    Cam resection (femoroplasty), rim trimming (acetabuloplasty) and labral repair or reconstruction under a designated hip preservation service (see /treatments/hip-arthroscopy-fai/).

  • Periacetabular osteotomy

    Bernese PAO for underlying acetabular dysplasia - specialist hip preservation surgery in a small number of UK centres.

  • Total hip replacement

    Reserved for advanced secondary osteoarthritis - a highly effective operation when joint preservation is no longer possible (see /treatments/total-hip-replacement/).

What this guide is based on

The sources behind every claim on this page.

UK national guidance, specialist society standards and landmark trials, current at the time of last review.

Key references

Guidelines and trials we relied on.

A quiet reminder

This guide is for information, not medical advice.

Your GP or hip preservation specialist knows your history and imaging and can tell you which parts apply to you. If in doubt, get seen.

  • Griffin DR et al. FASHIoN trial - hip arthroscopy versus best conservative care for FAI syndrome. The Lancet, 2018.

  • Warwick Agreement on femoroacetabular impingement syndrome (2016).

  • British Hip Society (BHS) and British Orthopaedic Association (BOA) guidance on young adult hip disease.

  • NICE. Arthroscopic femoroacetabular surgery for hip impingement syndrome (IPG408).

Red flags

When hip pain needs urgent attention.

Most FAI is a slow-burn problem. These are the situations that are not, and where an urgent specialist opinion is needed.

  • Sudden severe hip pain

    Acute inability to weight-bear or trauma with severe groin pain needs urgent orthopaedic review to exclude fracture or dislocation.

  • Fever with hip pain

    Suspect septic arthritis - a same-day emergency needing joint aspiration and intravenous antibiotics.

  • Progressive night pain

    Unremitting rest and night pain, especially with weight loss, warrants urgent imaging to rule out bone tumours or metastases.

  • Cauda equina features

    Bilateral leg symptoms, saddle numbness or new bladder or bowel disturbance is a spinal emergency, not a hip problem.

  • Childhood hip disease

    A history of SCFE, Perthes or hip dysplasia raises the risk of FAI and needs a specialist young-adult hip opinion.

  • Rapidly progressive stiffness

    Quickly worsening stiffness with radiological joint space loss suggests established osteoarthritis rather than pure FAI.

  • Failed conservative care at six months

    Persistent limiting symptoms after a structured rehabilitation programme should trigger specialist hip preservation referral.

  • Groin lump or hernia

    Consider an inguinal or sports hernia as an alternative or coexistent cause - examine and image accordingly.

  • Bilateral disease in a young adult

    Bilateral FAI features or dysplasia raise the possibility of an underlying developmental hip disorder.

Living with it

A treatable hip, with a clear ladder.

Four things that make the biggest difference day to day - smart loading, specialist rehabilitation, better sitting habits and knowing when to escalate.

A quiet reminder

Consistency beats intensity, every time.

Small, steady habits and progressive rehabilitation do more for a hip than a heroic week of training that ends in a flare.

  1. 01 Load

    Manage load, don’t retire

    Modify provocative activities in the short term while you rebuild strength - most patients return to full sport with a proper plan.

  2. 02 Rehab

    Backed by a specialist physio

    Hip preservation physiotherapy targets gluteal control, deep core and pelvic mechanics - not generic hip stretches.

  3. 03 Sitting

    Change your sitting habits

    Break up long drives and desk sessions, and consider a slightly higher chair to open the hip angle.

  4. 04 Escalate

    Know when to escalate

    If symptoms persist after three to six months of good rehabilitation, ask for a specialist hip preservation review.

Frequently asked

Everything we get asked about FAI.

Quick answers on cam and pincer patterns, MRI arthrogram, hip arthroscopy and long-term outcomes.

  • What is femoroacetabular impingement (FAI)?

    FAI is a shape-based mismatch between the ball (femoral head-neck junction) and socket (acetabulum) of the hip. At end-range positions the two surfaces pinch, which over time tears the labrum, damages cartilage and can lead to early osteoarthritis. It is one of the commonest reasons for hip pain in active young adults.

  • What are the different types of FAI?

    There are three patterns. Cam impingement is caused by a non-spherical femoral head-neck junction and is most common in young male athletes. Pincer impingement is caused by over-coverage of the socket - a deep or retroverted acetabulum - and is more common in women in mid-life. Combined impingement, where both features coexist, accounts for around 85% of symptomatic cases.

  • How is FAI diagnosed?

    Diagnosis combines a targeted history, examination (a positive FADIR test and reduced internal rotation are typical) and imaging. Plain radiographs (AP pelvis, Dunn view and false profile) measure the alpha angle and centre-edge angle. An MRI arthrogram is the reference test for labral tears and cartilage damage and is normally arranged by a specialist hip preservation service.

  • Does everyone with FAI on imaging need surgery?

    No. Radiographic FAI is common and often asymptomatic. Surgery is only considered for people with symptoms, a supportive examination and imaging, and whose symptoms have not settled with a proper course of activity change, physiotherapy and, sometimes, an image-guided joint injection.

  • What does hip arthroscopy for FAI involve?

    Hip arthroscopy is keyhole surgery to reshape the femoral head-neck junction (femoroplasty), trim the acetabular rim (acetabuloplasty) if needed, and repair or reconstruct the labrum. The FASHIoN trial showed better outcomes than conservative care for symptomatic FAI syndrome at 12 months. Recovery to full sport typically takes 6 to 12 months with specialist rehabilitation.

  • Will FAI cause hip osteoarthritis?

    Untreated symptomatic FAI is a recognised risk factor for premature hip osteoarthritis, particularly in cam-type disease. The aim of hip preservation - through physiotherapy, activity change and, where indicated, arthroscopic surgery - is to protect the cartilage and delay or avoid the need for a hip replacement.

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