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Health condition · Clinically reviewed

Hip impingement, the Warwick triad, arthroscopy and hip preservation.

Deep groin pain in a young active adult is often femoroacetabular impingement. A specialist hip preservation pathway saves cartilage - and options.

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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 registered UK clinician before publication.

  • 02

    Sourced from guidance

    Checked against the Warwick Agreement, BOA and peer-reviewed hip preservation sources.

  • 03

    Current for 2026

    Reflects the specialist commissioned hip preservation pathway, arthroscopy, PAO and MDT working in the UK.

Key facts

Hip impingement at a glance.

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

  • What it is

    Femoroacetabular impingement (FAI) - abnormal contact between the femoral head-neck junction and the acetabular rim, injuring the labrum and cartilage.

  • Types

    CAM (aspherical femoral head-neck), PINCER (acetabular over-coverage) and MIXED - the mixed pattern is the most common in adults.

  • Who it affects

    Young active adults - CAM tends to affect athletic men, PINCER middle-aged women. Youth sport, Perthes and SUFE are risk factors.

  • How it presents

    Deep hip or groin pain, worse with sitting, squatting and pivoting - often with a positive FADIR test on examination.

  • Gold-standard scan

    MRI arthrogram - the definitive test for labral and chondral injury, done in a specialist hip preservation centre.

  • Treatment ladder

    Specialist physiotherapy first, then hip arthroscopy for structural cases. Selective surgical dislocation or PAO where indicated.

Why this guide matters

A hip preservation pathway, not a waiting game.

FAI is common, treatable and time-sensitive - untreated CAM impingement drives early osteoarthritis. Three points frame everything on this page.

  • The Warwick triad matters

    A diagnosis of FAI syndrome needs symptoms, clinical signs and imaging that fit - not imaging alone. Bumps on a scan without symptoms do not need surgery.

  • Rehab first, in expert hands

    A structured 12-week physiotherapy programme with a hip preservation specialist changes symptoms for many patients - and improves outcomes if surgery follows.

  • The right operation, the right centre

    Hip arthroscopy, PAO and surgical dislocation are specialist commissioned procedures. Outcomes are best in high-volume UK hip preservation units.

How the diagnosis is made

From first groin twinge to an MDT plan.

The steps a UK hip preservation team will normally follow, in order - so you know what to expect and why each stage matters.

  1. 01

    Assessing

    History and activity profile

    Deep hip or groin pain, worse with sitting, squatting or pivoting - and the sports or work that reproduce it. Onset in adolescence or early adult life is typical.

  2. 02

    Assessing

    Examination - FADIR and FABER

    Flexion-adduction-internal-rotation reproduces impingement pain. FABER localises posterior or sacroiliac pain. Internal rotation is characteristically reduced.

  3. 03

    Assessing

    Plain X-ray - alpha angle

    AP pelvis and Dunn lateral views. An alpha angle greater than 55 degrees suggests CAM morphology. A crossover sign points to PINCER over-coverage.

  4. 04

    Confirming

    MRI arthrogram

    The gold standard for labral tears and chondral loss - and for planning surgery. See our guide to the /treatments/mri-arthrogram/ for what the scan involves.

  5. 05

    Confirming

    Diagnostic intra-articular block

    A guided local anaesthetic injection into the hip joint - if pain settles for a few hours, the pain is coming from inside the joint.

  6. 06

    Preparing

    Hip preservation MDT review

    Complex cases are discussed in a specialist commissioned hip preservation MDT - Warwick, Oxford, Great Ormond Street and other designated UK centres.

  7. 07

    Preparing

    Shared decision - Warwick agreement

    The Warwick Agreement frames FAI as a triad of symptoms, signs and imaging. All three must fit before considering surgery.

Typical timeline: a first visit to a settled MDT plan in a few weeks, once the imaging is complete.

Symptoms

What hip impingement actually feels like.

Deep groin pain with sitting, squatting and pivoting - the classic pattern in a young athletic hip. And the signs that mean it is time to escalate.

  • Deep groin or hip pain

    A deep, sharp or aching pain in the groin - often pointed to with a C-shaped grip around the hip (the "C-sign").

  • Pain with sitting and squatting

    Long car journeys, low sofas, deep squats and yoga positions reliably reproduce the pain.

  • Catching, clicking or locking

    Mechanical symptoms suggest an associated labral tear - see our guide to /conditions/hip-labral-tear/.

  • Reduced deep flexion and rotation

    Loss of internal rotation is the most sensitive clinical sign - patients often notice it in pilates or on the football pitch.

  • Activity-related pain

    Symptoms build during and after sport - pivoting, kicking and change-of-direction sports are typical triggers.

  • Stiffness in the morning

    Short-lived stiffness after rest that eases with movement - not the prolonged stiffness of inflammatory arthritis.

  • Young and athletic

    Most patients are in their 20s to 40s - the age when a structural hip problem meets a demanding activity level.

  • Red flag - progressive limp

    A worsening limp, night pain or referred knee pain deserves early hip preservation review before cartilage is lost.

Treatment

How hip impingement is treated in the UK.

Specialist physiotherapy first - then arthroscopy, PAO or surgical dislocation for structural cases, and replacement once osteoarthritis is established.

  • Specialist musculoskeletal physiotherapy

    The evidence-based first step - core, glute and neuromuscular retraining, plus activity modification. Best delivered by a hip preservation specialist physiotherapist.

  • Activity modification

    Reducing deep flexion, prolonged sitting and repetitive pivoting - a temporary reset while strength and control are rebuilt.

  • NSAIDs

    Short courses of anti-inflammatories can help symptomatic flares - not a long-term solution and not a substitute for rehab.

  • Image-guided steroid injection

    Selective use in the joint - useful diagnostically and for short-term symptom control before or instead of surgery.

  • Hip arthroscopy

    Keyhole surgery to reshape the femoral head-neck (femoroplasty) and rim (acetabuloplasty), and to repair or reconstruct the labrum. See /treatments/hip-arthroscopy/.

  • Periacetabular osteotomy (PAO)

    For dysplasia with a secondary impingement pattern - the acetabulum is reoriented over the femoral head. See /treatments/periacetabular-osteotomy/.

  • Surgical hip dislocation

    A specialist open procedure reserved for complex deformity - performed only in designated hip preservation centres.

  • Total hip replacement

    When impingement has driven established osteoarthritis, a replacement gives a reliable and durable result. See /treatments/hip-replacement-surgery/.

What this guide is based on

The sources behind every claim on this page.

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

Key references

Guidelines and standards we relied on.

A quiet reminder

This guide is for information, not medical advice.

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

  • The Warwick Agreement on femoroacetabular impingement syndrome (BJSM, consensus statement).

  • British Orthopaedic Association (BOA). Standards for hip preservation surgery.

  • NHS England. Specialist commissioned hip preservation service specification.

  • Griffin DR et al. FASHIoN trial - hip arthroscopy versus physiotherapy for FAI syndrome (The Lancet).

Red flags

When hip pain needs urgent attention.

Most FAI is managed by a hip preservation team over weeks and months. These are the situations that will not wait - and where a specialist opinion is needed sooner.

  • Night pain and rest pain

    Pain that wakes you from sleep or is present at rest is not typical of mechanical impingement - it warrants an urgent hip preservation review to exclude other causes.

  • Progressive limp

    A worsening antalgic gait suggests advancing cartilage loss - early referral is important before osteoarthritis becomes established.

  • True locking of the hip

    A hip that catches and will not move is a mechanical block - most often an unstable labral tear. Prompt hip preservation review is needed.

  • Constitutional symptoms

    Fever, weight loss or malaise with hip pain is not FAI - urgent investigation for infection, inflammation or tumour is required.

  • Adolescent hip pain with a limp

    A limping teenager with hip or knee pain must be assessed urgently for slipped upper femoral epiphysis (SUFE) before it becomes irreducible.

  • Hip pain after childhood Perthes

    A history of Perthes disease sharply increases the risk of a complex CAM deformity - early hip preservation review is prudent.

  • Groin pain in a female runner

    Consider a femoral neck stress fracture alongside FAI - the two can coexist and the fracture must not be missed.

  • Bilateral disabling hip pain

    Bilateral disease with severe stiffness deserves early rheumatology input to exclude an inflammatory arthropathy.

  • Referred pain from the spine

    Not every groin pain is a hip - lumbar radiculopathy and sacroiliac disease can mimic FAI and need careful examination.

Living with it

A treatable hip, with a clear ladder.

Four principles that make the biggest difference - staying active inside your envelope, respecting rehab, knowing when to image and matching the operation to the problem.

A quiet reminder

Preservation, not perfection.

The aim of a hip preservation pathway is to keep your own joint working well for as long as possible - not to chase a perfect scan.

  1. 01 Move

    Keep moving inside your envelope

    Low-impact aerobic exercise, guided strength work and mobility drills keep the joint healthy while surgery is planned or avoided.

  2. 02 Rehab

    Physiotherapy is not a warm-up

    A structured 12-week programme with a hip preservation specialist physiotherapist is a treatment in its own right - not something to rush.

  3. 03 Escalate

    Know when to ask for imaging

    If symptoms persist beyond 3 to 6 months of good rehab, an MRI arthrogram and a hip preservation opinion are reasonable next steps.

  4. 04 Decisions

    Match the operation to the problem

    Arthroscopy, PAO and replacement solve different problems - the right choice needs an MDT that sees enough hips to know the difference.

Frequently asked

Everything we get asked about hip impingement.

Quick answers on the Warwick triad, MRI arthrogram, hip arthroscopy and when preservation becomes replacement.

  • What is hip impingement?

    Femoroacetabular impingement, or FAI, is abnormal contact between the femoral head-neck junction and the rim of the socket during deep hip movement. Repeated contact injures the labrum and the cartilage, and over time can lead to early osteoarthritis. The Warwick Agreement defines the syndrome as a triad of symptoms, clinical signs and imaging findings.

  • What are the different types of FAI?

    There are three patterns. CAM impingement is an aspherical bump at the femoral head-neck junction, typically in young active men. PINCER impingement is over-coverage of the socket, more common in middle-aged women. Mixed impingement combines both - and is the most common pattern seen in adults presenting with symptoms.

  • How is FAI diagnosed?

    A careful history and examination come first - deep groin pain, a positive FADIR test and reduced internal rotation are typical. Plain X-rays show the alpha angle and any crossover sign. An MRI arthrogram is the gold standard for looking at the labrum and cartilage, and it is the test that specialist commissioned hip preservation centres rely on when planning surgery.

  • Do I need surgery for hip impingement?

    Not always. Specialist musculoskeletal physiotherapy, activity modification and selective injections work well for many people. The FASHIoN trial showed hip arthroscopy is more effective than physiotherapy alone for structural FAI syndrome, but decisions are always shared and made in a hip preservation MDT that sees all three parts of the Warwick triad.

  • What does hip arthroscopy involve?

    A keyhole operation performed in a specialist commissioned centre. The surgeon reshapes the femoral head-neck (femoroplasty) and, where needed, trims the acetabular rim (acetabuloplasty). The labrum is repaired or reconstructed. Recovery is around 3 to 6 months, with a structured rehabilitation programme. Read more in our guide to /treatments/hip-arthroscopy/.

  • Can FAI cause hip arthritis?

    Yes. Untreated CAM impingement in particular is associated with early cartilage loss and osteoarthritis, especially in active adults. That is why timely diagnosis and preservation surgery matter. Once osteoarthritis is established, the conversation shifts from preservation to /treatments/hip-replacement-surgery/.

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