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Health condition · Clinically reviewed

Patellofemoral pain syndrome, runner’s knee explained - and how it’s actually rehabilitated.

Diffuse anterior knee pain that flares with running, squats and stairs. A structured strengthening plan beats rest alone.

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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 BMJ Best Practice, sports medicine consensus statements and peer-reviewed sources you can see at the end.

  • 03

    Current for 2026

    Reflects modern rehabilitation-first practice, including hip strengthening and graded return to running.

Key facts

Patellofemoral pain at a glance.

The essentials, in plain English - what it is, who it affects, and how it’s treated.

  • What it is

    Diffuse anterior knee pain from abnormal tracking or loading of the kneecap against the femoral groove - often called runner’s knee.

  • Who it affects

    Very common in young, active people and runners, particularly those increasing training load quickly.

  • Cause

    Usually multifactorial - weak hip and quadriceps muscles, biomechanical factors and training errors, rather than one single problem.

  • Typical triggers

    Running, squatting, descending stairs and prolonged sitting with bent knees - the so-called "theatre sign".

  • No instability

    Grinding or crepitus is common, but true giving way or instability is not typical and points elsewhere.

  • Foundation therapy

    Activity modification plus physiotherapy focused on hip and quadriceps strengthening - surgery is rarely needed.

Why this guide matters

A rehab plan, not just rest.

Patellofemoral pain is common, treatable and usually settles with the right approach. The three points below shape everything else on this page.

  • It’s rarely one single cause

    Muscle imbalance, biomechanics and training errors usually combine - which is why a broad assessment matters more than a single test.

  • Hip and quadriceps strength is key

    Weak hip abductors and external rotators are consistently linked to patellofemoral pain, and strengthening them is central to recovery.

  • Complete rest rarely helps long-term

    Reducing load while staying active, then building back up gradually, beats stopping activity altogether.

How the diagnosis is made

From first ache to a clear plan.

The steps a UK GP, physiotherapist or sports medicine clinician will normally follow, in order - so you know what to expect and why.

  1. 01

    Assessing

    Detailed history

    Pattern of pain, training changes, footwear and aggravating activities - running, squatting, stairs, sitting.

  2. 02

    Assessing

    Anterior knee examination

    Palpation around the kneecap, patellar tracking through range of movement, and assessment for effusion.

  3. 03

    Assessing

    Hip and quadriceps strength

    Specific testing of hip abductor and external rotator strength - consistently linked to patellofemoral pain.

  4. 04

    Confirming

    Biomechanical assessment

    Looking at foot posture, knee alignment and running gait, since these can drive abnormal patellar loading.

  5. 05

    Confirming

    Excluding instability

    Checking apprehension and laxity to rule out true patellar instability, which needs a different pathway.

  6. 06

    Preparing

    Imaging only if atypical

    X-ray or MRI is reserved for atypical features, red flags, or when the diagnosis remains uncertain after assessment.

  7. 07

    Preparing

    Agreeing a rehab plan

    Confirming the working diagnosis and starting a structured, graded strengthening and loading programme.

Typical timeline: a first visit to a settled rehab plan within a week or two.

Symptoms

What patellofemoral pain actually feels like.

A recognisable pattern of anterior knee pain with certain reliable triggers. And the features that mean it’s worth a fuller assessment.

  • Diffuse anterior knee pain

    Pain around or behind the kneecap that is often hard to pinpoint to one exact spot - peripatellar rather than sharply localised.

  • Worse with running

    A classic trigger, especially with sudden increases in distance, speed or hill work.

  • Worse with squatting

    Deep knee bend loads the patellofemoral joint directly and reliably reproduces the pain.

  • Worse descending stairs

    Going down stairs loads the joint more than going up, which is a useful clue in the history.

  • Theatre sign

    Aching after sitting with bent knees for a long time - at the cinema, on a flight or at a desk.

  • Grinding or crepitus

    A sensation of grinding, clicking or crunching under the kneecap during movement.

  • No true instability

    Unlike patellar instability, there is usually no sense of the kneecap actually giving way or slipping out.

  • Red flag - swelling or locking

    Significant swelling, locking or a sense of the knee giving way needs a fuller assessment for other causes.

Treatment

How patellofemoral pain is treated.

Activity modification and targeted strengthening first, with taping, orthotics and analgesia as adjuncts - surgery only for refractory cases.

  • Activity modification

    Reduce aggravating loaded activities rather than stopping completely - relative rest, not complete rest, keeps the joint moving.

  • Hip strengthening

    Targeted hip abductor and external rotator work - one of the best-evidenced elements of a rehabilitation programme.

  • Quadriceps strengthening

    Progressive loading of the quadriceps, particularly closed-chain exercises, to support the patella through its range.

  • Biomechanical review

    Assessing foot posture and running technique - foot orthotics can help selected patients with a clear biomechanical driver.

  • Patellar taping or bracing

    Used as an adjunct alongside exercise, not instead of it - can reduce pain enough to allow strengthening to progress.

  • Ice and analgesia

    Simple measures for symptomatic relief during flare-ups, alongside the ongoing strengthening programme.

  • Graded return to activity

    A staged increase in running or sport, guided by symptoms, once strength and control have improved.

  • Surgery - rarely needed

    Reserved for refractory cases with a clear structural cause, after a full course of guided rehabilitation has failed.

What this guide is based on

The sources behind every claim on this page.

UK and international sports medicine guidance and specialist consensus, 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 physiotherapist knows your knee and history and can tell you which parts apply to you. If in doubt, get seen.

  • BMJ Best Practice. Patellofemoral pain syndrome.

  • 2018 International Patellofemoral Pain Research Retreat consensus statement.

  • Chartered Society of Physiotherapy. Guidance on anterior knee pain rehabilitation.

  • British Journal of Sports Medicine. Exercise therapy for patellofemoral pain.

Red flags

When knee pain needs more than reassurance.

Most anterior knee pain is patellofemoral and manageable in primary care. These are the situations that aren’t - and where a fuller assessment is needed.

  • Significant joint swelling

    A tense or rapidly swelling knee is not typical of patellofemoral pain and needs assessment for another cause.

  • True locking

    The knee genuinely catching or locking suggests a mechanical block such as a meniscal tear, not patellofemoral pain.

  • A sense of the kneecap giving way

    This points towards patellar instability rather than patellofemoral pain syndrome and needs a different assessment pathway.

  • Night pain or systemic symptoms

    Pain that wakes you at night, fevers or unexplained weight loss are not typical and warrant wider investigation.

  • Sudden severe pain after trauma

    A significant injury with immediate severe pain and swelling needs urgent assessment for fracture or ligament injury.

  • Symptoms not settling with rehabilitation

    Failure to improve after a properly supervised strengthening programme deserves specialist sports medicine or orthopaedic review.

  • Marked quadriceps wasting

    Visible muscle wasting alongside pain can suggest a more longstanding or different underlying problem.

  • Bilateral progressive pain in a child

    In younger patients, progressive bilateral anterior knee pain should prompt review for other paediatric causes.

Living with it

A treatable condition, with a clear ladder.

Four things that make the biggest difference day to day - sensible load management, consistent strengthening, breaking up long sits and a gradual return to sport.

A quiet reminder

Consistency beats intensity, every time.

Small, steady habits - kept up for weeks - do more for a knee than a heroic session that leaves it flared up.

  1. 01 Load

    Reduce, don’t eliminate

    Cut back on the activities that flare things up rather than stopping exercise altogether - staying active supports recovery.

  2. 02 Strength

    Commit to the exercises

    Hip and quadriceps strengthening works, but needs weeks of consistent effort - short bursts rarely help.

  3. 03 Sitting

    Break up long sits

    Straighten the knee or stand up periodically during long periods of sitting to ease the theatre sign.

  4. 04 Return

    Build back up gradually

    When returning to running or sport, increase distance or intensity gradually rather than jumping back to previous levels.

Frequently asked

Everything we get asked about runner’s knee.

Quick answers on causes, imaging, running, hip strengthening and surgery.

  • What is patellofemoral pain syndrome?

    A very common cause of anterior knee pain from abnormal tracking or loading of the kneecap against the femoral groove. It is often multifactorial, involving muscle imbalance, biomechanical factors and training errors, and is sometimes called runner’s knee.

  • Is patellofemoral pain the same as patellar instability?

    No. Patellofemoral pain syndrome causes diffuse aching and grinding without true instability. Patellar instability involves a sense of the kneecap actually giving way or slipping, and is assessed and managed differently.

  • Do I need an X-ray or MRI?

    Usually not. The diagnosis is normally made clinically from the pattern of pain and examination findings. Imaging is reserved for atypical presentations or when the diagnosis is uncertain after assessment.

  • Should I stop running completely?

    Generally not. Complete rest is rarely necessary - the usual approach is to reduce the aggravating load, such as distance or intensity, while starting a strengthening programme, then build back up gradually.

  • Why does hip strengthening help a knee problem?

    Weakness in the hip abductor and external rotator muscles is strongly linked to patellofemoral pain, because it changes how load passes through the knee. Strengthening these muscles is one of the best-evidenced parts of treatment.

  • Will I need surgery?

    Surgery is rarely needed. Most people improve with activity modification and a structured physiotherapy programme. Surgery is reserved for refractory cases with a clear structural cause after rehabilitation has been tried properly.

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