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Health condition · Clinically reviewed

Knee bursitis, the swollen sac in front of, behind or beside the knee.

Most cases settle with simple measures. Some need an image-guided injection. A few - the hot, red, feverish ones - need urgent specialist care.

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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 NICE, BOA and peer-reviewed musculoskeletal sources you can see at the end.

  • 03

    Current for 2026

    Reflects modern UK practice including image-guided injection and septic bursitis pathways.

Key facts

Knee bursitis at a glance.

The essentials, in plain English - what a bursa is, which ones inflame around the knee, and how it is treated in the UK today.

  • What it is

    Inflammation of one of the fluid-filled bursae that cushion tendons and bones around the knee.

  • Common types

    Prepatellar (housemaid's knee), infrapatellar (clergyman's knee), pes anserinus and semimembranosus (Baker's cyst).

  • Who gets it

    Kneeling occupations, runners, people with overweight, and those with inflammatory arthritis or gout.

  • Key concern

    Septic bursitis - a red, hot, tender bursa with fever - is a specialist emergency needing urgent care.

  • First-line care

    Activity modification, knee pads, ice, NSAIDs and a short spell of rest often settle non-septic disease.

  • Escalation

    Image-guided steroid injection, aspiration and, rarely, surgical excision for refractory or septic cases.

Why this guide matters

A common problem, with a clear stepped plan.

Knee bursitis is common, treatable and mostly manageable in primary care. Three points shape the rest of this page.

  • Most cases settle with simple measures

    Activity modification, knee pads, ice and a short course of NSAIDs resolve the majority of non-septic bursitis within weeks.

  • Image-guided injection helps stubborn cases

    When bursitis refuses to settle, a specialist musculoskeletal steroid injection under ultrasound is often decisive - see the steroid injection guide.

  • Septic bursitis is an emergency

    A hot, red, feverish knee needs same-day specialist assessment - aspiration, culture and antibiotics.

How the diagnosis is made

From first swelling to a clear plan.

The steps a UK GP or musculoskeletal specialist will normally follow, in order - so you know what to expect and why.

  1. 01

    Assessing

    History and occupation

    A careful history covering kneeling work, trauma, running load, gout or inflammatory arthritis - and red flags for infection.

  2. 02

    Assessing

    Focused examination

    Palpation of each bursa in turn, range of movement, and specific tests to separate bursitis from deep knee joint pathology.

  3. 03

    Assessing

    Rule out septic bursitis

    Warmth, redness, fever and severe tenderness raise concern - a specialist emergency review is needed the same day.

  4. 04

    Confirming

    Ultrasound assessment

    A musculoskeletal ultrasound scan shows bursal fluid, thickening and any deeper tendon problem, and guides aspiration or injection.

  5. 05

    Confirming

    MRI where selective

    A private MRI scan is reserved for atypical, deep or refractory disease to look for an underlying cause.

  6. 06

    Preparing

    Aspiration and culture

    If septic bursitis is suspected, specialist aspiration with fluid microscopy, culture and sensitivity is essential.

  7. 07

    Preparing

    Serology and urate

    When gout or an inflammatory arthritis is possible, blood tests including urate and inflammatory markers are requested.

Typical timeline: from first appointment to settled plan in a matter of weeks.

Symptoms

What knee bursitis actually feels like.

A pattern of focal swelling and tenderness that depends on which bursa is inflamed - and the features that mean it is time to escalate.

  • Prepatellar swelling

    A well-defined swelling right in front of the kneecap - housemaid's knee, classic in kneeling occupations.

  • Infrapatellar tenderness

    Pain and swelling just below the kneecap - superficial (clergyman's knee) or deep to the patellar tendon.

  • Pes anserinus pain

    Tenderness on the inner side of the knee, two to three fingers below the joint line - common in runners and overweight women.

  • Popliteal swelling

    A soft swelling behind the knee suggests a Baker's cyst arising from the semimembranosus bursa.

  • Limited knee flexion

    Bending the knee stretches the inflamed bursa and reproduces pain - full squatting is often impossible.

  • Warmth over the bursa

    Modest local warmth is common in inflammatory bursitis - marked heat with fever suggests infection.

  • Occupational pattern

    Carpet layers, plumbers, roofers, gardeners and clergy have a well-recognised, avoidable pattern of disease.

  • Red flag - septic bursitis

    Hot, red, exquisitely tender knee with fever or systemic upset needs urgent specialist assessment the same day.

Treatment

How knee bursitis is treated in the UK.

Simple measures first, image-guided injection or aspiration next, and specialist surgery reserved for refractory or septic disease.

  • Activity modification

    Avoid prolonged kneeling and heavy squatting while the bursa settles - and rework the task if it triggered the flare.

  • Knee pads and cushioning

    Purpose-made kneeling pads distribute pressure and are the single most useful preventive step for kneeling trades.

  • Ice, rest, compression, elevation

    Simple RICE measures ease early bursitis and reduce swelling - most non-septic cases settle within two to six weeks.

  • NSAIDs and analgesia

    A short course of a non-steroidal anti-inflammatory alongside paracetamol is a reasonable first medical step.

  • Aspiration

    A specialist can drain a tense or painful bursa and send fluid for analysis if infection or crystal disease is possible.

  • Image-guided steroid injection

    A specialist musculoskeletal steroid injection under ultrasound is effective for stubborn, sterile bursitis.

  • Antibiotics for septic bursitis

    Flucloxacillin, guided by culture, is the mainstay - always under specialist supervision, sometimes as an inpatient.

  • Physiotherapy

    Guided rehabilitation from a musculoskeletal physiotherapist restores strength, control and pain-free load.

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 musculoskeletal specialist knows your knee and history and can tell you which parts apply to you. If in doubt, get seen.

  • NICE Clinical Knowledge Summaries. Bursitis.

  • British Orthopaedic Association. Standards for musculoskeletal care.

  • Royal College of General Practitioners. Common knee problems in primary care.

  • European Society of Musculoskeletal Radiology. Guidance on ultrasound-guided injection.

Red flags

When knee bursitis needs urgent attention.

Most knee bursitis is manageable in primary care. These are the situations that are not - and where a specialist opinion is needed.

  • Septic bursitis

    Hot, red, exquisitely tender bursa with fever or systemic upset - a specialist emergency requiring same-day review and often admission.

  • Rapidly spreading redness

    Cellulitis around the bursa needs prompt antibiotics and specialist assessment to prevent deeper infection.

  • Recent penetrating injury

    A cut, graze or puncture over the bursa raises the risk of infection - low threshold for a specialist opinion.

  • Immunosuppression

    Diabetes, steroid therapy or a suppressed immune system lowers the threshold for admission and intravenous antibiotics.

  • Deep joint involvement

    Locked knee, giving way or a large effusion suggests intra-articular pathology beyond a simple bursitis - specialist review.

  • Suspected gout or inflammatory disease

    Recurrent bursitis with hot joints elsewhere may reflect gout or an inflammatory arthritis - see the gout guide.

  • Failure to settle at six weeks

    Persistent bursitis despite conservative care warrants imaging, aspiration or specialist musculoskeletal input.

  • Popliteal mass with calf swelling

    A ruptured Baker's cyst can mimic a deep vein thrombosis - urgent assessment is needed to exclude clot.

  • Loss of sensation or weakness

    Any neurological change around the knee needs prompt specialist review to exclude nerve involvement.

Living with it

A treatable condition, with a clear ladder.

Four things that make the biggest difference day to day - protect the knee, keep moving, watch for infection and escalate early when needed.

A quiet reminder

Small changes at work matter most.

A pair of decent knee pads and a task rethink often does more than any single treatment.

  1. 01 Prevent

    Protect the knee

    If kneeling is part of your day, wear knee pads and take pressure off the front of the knee as often as you can.

  2. 02 Pace

    Modify, don't stop

    Most people can stay active - short walks, cycling and swimming often feel better than complete rest.

  3. 03 Warn

    Watch for infection

    A knee that becomes hotter, redder or more painful, especially with fever, needs same-day specialist advice.

  4. 04 Escalate

    Get a specialist opinion

    If pain lingers past six weeks, or you keep flaring, an image-guided injection or physiotherapy plan usually helps.

Frequently asked

Everything we get asked about knee bursitis.

Quick answers on the different types, scans, injections and when to worry.

  • What is knee bursitis?

    Knee bursitis is inflammation of one of the small fluid-filled sacs (bursae) that cushion the knee. The commonest types are prepatellar (housemaid's knee), infrapatellar (clergyman's knee), pes anserinus on the inner side, and semimembranosus behind the knee - a Baker's cyst.

  • What causes knee bursitis?

    Repeated kneeling and direct trauma are the classic causes, alongside running overload, obesity, inflammatory arthritis such as rheumatoid disease, and gout. A minority of cases are septic - caused by infection - and these need urgent specialist assessment.

  • How is knee bursitis different from arthritis of the knee?

    Bursitis inflames a bursa outside the joint, so swelling and tenderness are usually focal and superficial. Arthritis of the knee involves the joint itself, tends to cause stiffness, deeper pain and a joint effusion, and is diagnosed on examination and imaging - see the knee arthritis guide for detail.

  • When do I need a scan?

    Most cases are diagnosed clinically. Ultrasound is used to confirm bursal fluid, guide aspiration or injection, and rule out tendon problems. MRI is reserved for atypical, deep or refractory disease, or when a deeper injury is suspected.

  • How is bursitis treated?

    Activity modification, knee pads, ice, a short course of NSAIDs and rest settle most cases. Stubborn bursitis often responds to an image-guided steroid injection from a musculoskeletal specialist. Septic bursitis needs aspiration and antibiotics, and sometimes surgery.

  • When should I worry about septic bursitis?

    A knee that is hot, red, exquisitely tender and swollen - especially with fever, chills or a recent cut over the joint - may be a septic bursitis. This is a specialist emergency and needs same-day assessment, aspiration and antibiotics.

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