Changes

June 2025 — reviewed. A literature search was conducted in June 2025 to identify evidence-based guidelines, UK policy, systematic reviews, and key randomized controlled trials published since the last revision of this topic. No major changes to recommendations have been made.

Update

Goals

To support primary healthcare professionals to:

• Make a diagnosis of Baker's cyst.
• Consider important differential diagnoses.
• Manage Baker's cysts in primary care.
• Arrange referral to secondary care where appropriate.

Outcome measures

Audit criteria

QOF indicators

QIPP - Options for local implementation

No QIPP indicators were found during the review of this topic.

NICE quality standards

No NICE quality standards were found during the review of this topic.

What is it?

• A Baker's cyst (also known as a popliteal cyst) is not a true cyst but a distension of the gastrocnemius-semimembranosus bursa behind the knee. 
  • In most cases, they appear between the tendons of the gastrocnemius and semimembranosus muscles on the medial side of the popliteal fossa, slightly distal to the central knee crease.
• Baker's cysts are described as primary or secondary. 
  • Primary cysts are idiopathic and have no communication between the bursa and the knee joint. They are not associated with disease of the knee joint and are found mainly in children.
  • Secondary cysts are associated with underlying intra-articular knee disorders (such as osteoarthritis or meniscal tears) and tend to have a communication between the bursa and the rest of the knee joint that allows synovial fluid to fill the cyst. Almost all Baker's cysts in adults are secondary cysts.

[Fritschy, 2006; Harcke, 2016; Zhou, 2016; Shah, 2017; Han, 2019]

What causes it?

• In children, the majority of Baker's cysts are primary. 
  • Development of primary Baker's cysts may be related to trauma or local irritation of the bursa.
  • Secondary cysts may occur with conditions affecting the joints, such as juvenile idiopathic arthritis and osteochondritis dissecans.
• In adults, Baker's cysts are usually secondary to:
  • Osteoarthritis or inflammatory arthropathies, such as rheumatoid arthritis. 
  • Meniscal tears.
  • Damage to the anterior cruciate ligament. 
• Other conditions that are associated with Baker's cysts include:
  • Charcot joint. 
  • Connective tissue disease, such as systemic lupus erythematosus. 
  • Gonococcal arthritis.
  • Gout. 
  • Pigmented villonodular synovitis.
  • Polyarthritis.
  • Reiter's syndrome. 
  • Septic arthritis.
  • Tuberculosis. 

[Handy, 2001; Fritschy, 2006; Alessi, 2012; Stein, 2013; Harcke, 2016; Dagur, 2017; Han, 2019; Hasan, 2025]

How common is it?

• The reported prevalence of Baker's cysts varies widely depending on the population studied, the definition used, and the diagnostic method [Herman, 2014]. 
  • A peak in incidence occurs between 4 and 7 years of age, with a larger peak between 35 and 70 years of age [Handy, 2001]. 
• Baker's cysts are uncommon in children [Fritschy, 2006].
  • The majority of cysts in children (95%) are primary [Alessi, 2012]. 
  • A prospective epidemiological study (n = 168) of asymptomatic children (aged under 15 years) without knee pathology, found a prevalence of 2.4% using ultrasound as the diagnostic tool [Seil, 1999]. 
  • A review of magnetic resonance imaging (MRI) of 393 children with knee pain identified Baker's cysts in 6.3% (n = 25). Of the children found to have Baker's cysts, two had osteochondritis dissecans and two had synovial disease (infection and juvenile rheumatoid arthritis); none of the children with Baker's cysts had an associated soft tissue injury [De Maeseneer, 1999]. 
• Reported prevalence in adults varies widely between studies.
  • One study reviewing MRIs of knees in adults (n = 1001) found asymptomatic Baker's cysts in 4.7% of people [Sansone, 1995]. 
  • Another study (n = 195 knees in 187 people) found asymptomatic Baker's cysts in 37% of people undergoing arthroscopy [Johnston, 1997]. 
  • A retrospective review of ultrasound reports of 1120 adults in a rheumatology clinic found that 12.9% had Baker's cysts. Of those with Baker's cysts, 50.6% had osteoarthritis of the knee, 20.6% had rheumatoid arthritis, and 13.9% had gout [Liao, 2010]. 
  • There is no consistent difference between the sexes in the incidence of Baker's cyst in adults [Handy, 2001; Chatzopoulos et al, 2008].

What are the complications?

• Most Baker's cysts are not associated with complications.
• Complications of Baker's cyst include:
  • Chronic pain.
  • Dissection or rupture 
    • The most common complication is rupture, which may be asymptomatic in up to 80% of people. Cyst rupture is more likely to occur in people with underlying inflammatory conditions (such as rheumatoid arthritis or seronegative arthropathy) than in those with osteoarthritis. 
    • Dissection can occur when a cyst expands into the adjacent proximal gastrocnemius muscle belly, causing pain, warmth, tenderness, and redness of the calf. Rupture (with a sudden worsening of symptoms) may follow. This is known as pseudo-thrombophlebitis syndrome and can be difficult to distinguish clinically from deep vein thrombosis (DVT). 
  • Haemorrhage may occur, in particular in people taking anticoagulants.
  • Compression of adjacent structures may result in:
    • DVT (due to compression of the popliteal vein). 
    • Compartment syndrome (if pressure increases significantly following rupture of a cyst and dissection of synovial fluid into the posterior calf muscles). 
    • Lower limb ischaemia (due to compression of the popliteal artery). 
    • Nerve entrapment symptoms. 
  • Infection — can occur spontaneously or following corticosteroid injection.
  • Reduced mobility. 

[Handy, 2001; Fritschy, 2006; English, 2010; Hamlet, 2012; Herman, 2014]

What is the prognosis?

• Children
  • In the absence of underlying joint disease, many Baker's cysts resolve spontaneously and do not require intervention. Resolution may take a few years.
  • If there is underlying joint disease (such as juvenile arthritis), cysts tend to resolve when the underlying condition improves. 
• Adults
  • Spontaneous resolution is common without any treatment.
  • For people with an underlying knee joint condition, treatment of the condition often leads to regression of Baker's cysts. 
    • The severity of the underlying condition is an important prognostic factor for persistence of the cyst; in people with severe osteoarthritis, resolution of the cyst may be unrealistic.
  • Surgery is associated with a high recurrence rate and is usually reserved for large symptomatic cysts, or where it remains symptomatic after treatment of the underlying disorder, or where no origin has been found. 

[Rupp, 2002; Fritschy, 2006; English, 2010; Stein, 2013; Harcke, 2016]

How should I assess a person with a suspected Baker's cyst?

• Take a history, asking about:
  • Symptoms such as swelling and pain.
    • An asymptomatic swelling behind the knee may be the only feature. 
    • In children, Baker’s cysts are often found incidentally — the child or parent may report seeing or feeling a lump behind the knee.
    • In adults, non-specific posterior knee pain and a feeling of tightness are common. Pain may be due to the cyst itself or the underlying cause (for example, osteoarthritis or soft tissue injury). 
    • Symptoms may be aggravated by walking (as fluid passes between the knee joint and the cyst). Range of movement may be restricted by larger cysts. 
  • Possible underlying causes.
    • In adults, a Baker's cyst is almost always associated with another pathology of the knee joint, such as osteoarthritis or a meniscal tear. 
  • Complications and red flags.
    • Baker’s cysts are usually chronic but can present with acute symptoms if the cyst dissects or ruptures. Rupture can cause severe pain, with swelling, warmth, tenderness and erythema of the calf, and can mimic other serious conditions, such as deep vein thrombosis (DVT). 
    • Red flags indicating a serious cause of symptoms include a sudden increase in swelling or pain, a change in the consistency of a swelling, or neurovascular symptoms. 
• Examine the person standing and in the supine position.
  • Inspect and palpate the popliteal fossa for masses — assess the knee joint in full extension and at various degrees of flexion. 
    • Baker's cysts are typically visible as a bulge in the medial popliteal fossa (less often laterally) that is round, smooth, and fluctuant. They are most noticeable on standing and may be tender on palpation.
    • The cyst may feel tense in full knee extension and soften again or disappear when the knee is flexed, this is known as Foucher’s sign. 
    • Range of movement may be restricted, especially with larger cysts. 
    • Ruptured cysts present with calf pain (which is sometimes severe) and swelling — consider serious alternative diagnoses, such as DVT. 
  • Check for signs of alternative diagnoses that require urgent assessment in secondary care, such as DVT, compartment syndrome, septic arthritis, and joint instability or inability to weight bear following acute trauma.
    • For further information, see the CKS topics on Deep vein thrombosis and Knee pain - assessment.
  • Check for signs of underlying knee pathology, such as arthritis, joint instability, and ligament or meniscal damage. 
    • For further information, see the CKS topics on Osteoarthritis and Rheumatoid arthritis.
• Arrange investigations as appropriate:
  • In all children:
    • Ultrasound scan is recommended to confirm the diagnosis and rule out serious conditions, such as aneurysms of the popliteal artery, soft tissue tumours, or venous thrombosis. 
  • In adults:
    • History and examination may be sufficient to make the diagnosis, but imaging (with urgency depending on clinical judgement) may be needed for confirmation of diagnosis and exclusion of other serious conditions, such as DVT or popliteal artery aneurysm.
    • Ultrasound scan can be used to confirm diagnosis, evaluate complications (such as rupture or haemorrhage), and exclude DVT.
    • Plain X-ray of the knee is of limited value in confirming or excluding a diagnosis of Baker's cyst. It may be appropriate as part of an assessment of underlying knee joint disease.
    • MRI may be appropriate to identify underlying conditions, such as meniscal tear. 

What else might it be?

• The differential diagnosis of Baker's cyst includes:
  • Deep vein thrombosis — for further information, see the CKS topic on Deep vein thrombosis. 
  • Superficial thrombophlebitis — for further information, see the CKS topic on Superficial vein thrombosis (superficial thrombophlebitis). 
  • Abscess. 
  • Benign or malignant tumours (such as sarcoma, lymphoma or metastases). 
  • Ganglion cyst. 
  • Haematoma.
  • Lipoma. 
  • Meniscal cyst. 
  • Muscular herniation. 
  • Popliteal artery aneurysm. 
  • Popliteal varices. 
  • Synovial hemangioma. 

Scenario: Management of Baker's cyst

From birth onwards.

Paracetamol and non-steroidal anti-inflammatory drugs (NSAIDs)

For prescribing information on paracetamol and nonsteroidal anti-inflammatory drugs (NSAIDs), see the CKS topics on Analgesia - mild-to-moderate pain and NSAIDs - prescribing issues.

Search strategy

Scope of search

A literature search was conducted for guidelines and systematic reviews on primary care management of Baker's cyst.

Search dates

April 2020 - June 2025

Key search terms

The terms listed below are the core search terms that were used for EBSCOhost MEDLINE (searched 23rd April 2020). These were combined with filters to identify guidelines, systematic reviews and primary care relevant literature in EBSCOhost MEDLINE. The strategy was adapted for The Cochrane Library databases. 

S3     S1 OR S2
S2    AB ( ((popliteal OR baker*) N2 cyst*) ) OR TI ( ((popliteal OR baker*) N2 cyst*) ) 
S1    (MH "Popliteal Cyst") 

Sources of guidelines

• National Institute for Health and Care Excellence (NICE)
• Scottish Intercollegiate Guidelines Network (SIGN)
• Royal College of Physicians
• Royal College of General Practitioners
• Royal College of Nursing
• NICE Evidence
• World Health Organization
• Guidelines International Network
• TRIP database
• Agency for Healthcare Research and Quality
• National Health and Medical Research Council (Australia)
• Royal Australian College of General Practitioners
• British Columbia Medical Association
• Canadian Medical Association
• Alberta Medical Association
• Michigan Quality Improvement Consortium
• Singapore Ministry of Health
• National Resource for Infection Control
• RefHELP NHS Lothian Referral Guidelines
• Medline (with guideline filter)
• Driver and Vehicle Licensing Agency
• NHS Health at Work (occupational health practice)

Sources of systematic reviews and meta-analyses

• The Cochrane Library:
  • Systematic reviews
  • Protocols
  • Database of Abstracts of Reviews of Effects
• Medline (with systematic review filter)
• EMBASE (with systematic review filter)

Sources of health technology assessments and economic appraisals

• NIHR Health Technology Assessment programme
• The Cochrane Library:
  • NHS Economic Evaluations
  • Health Technology Assessments
• Canadian Agency for Drugs and Technologies in Health
• International Network of Agencies for Health Technology Assessment

Sources of randomized controlled trials

• The Cochrane Library:
  • Central Register of Controlled Trials
• Medline (with randomized controlled trial filter)
• EMBASE (with randomized controlled trial filter)

Sources of evidence based reviews and evidence summaries

• Drug and Therapeutics Bulletin
• TRIP database
• Central Services Agency COMPASS Therapeutic Notes

Sources of national policy

• Department of Health
• Health Management Information Consortium (HMIC)

Patient experiences

• Healthtalk
• BMJ - Patient Journeys

Sources of medicines information

The following sources are used by CKS pharmacists and are not necessarily searched by CKS information specialists for all topics. Some of these resources are not freely available and require subscriptions to access content.

• British National Formulary (BNF)
• electronic Medicines Compendium (eMC)
• European Medicines Agency (EMEA)
• Medicines and Healthcare products Regulatory Agency (MHRA)
• REPROTOX
• Scottish Medicines Consortium
• Stockley's Drug Interactions
• TERIS
• TOXBASE
• Micromedex
• UK Medicines Information

Stakeholder engagement

Our policy

The external review process is an essential part of CKS topic development. Consultation with a wide range of stakeholders provides quality assurance of the topic in terms of:

• Clinical accuracy.
• Consistency with other providers of clinical knowledge for primary care.
• Accuracy of implementation of national guidance (in particular NICE guidelines).
• Usability.

Principles of the consultation process

• The process is inclusive and any individual may participate.
• To participate, an individual must declare whether they have any competing interests or not. If they do not declare whether or not they have competing interests, their comments will not be considered.
• Comments received after the deadline will be considered, but they may not be acted upon before the clinical topic is issued onto the website.
• Comments are accepted in any format that is convenient to the reviewer, although an electronic format is encouraged.
• External reviewers are not paid for commenting on the draft topics.
• Discussion with an individual or an organization about the CKS response to their comments is only undertaken in exceptional circumstances (at the discretion of the Clinical Editor or Editorial Steering Group).
• All reviewers are thanked and offered a letter acknowledging their contribution for the purposes of appraisal/revalidation.
• All reviewers are invited to be acknowledged on the website. All reviewers are given the opportunity to feedback about the external review process, enabling improvements to be made where appropriate.

Stakeholders

• Key stakeholders identified by the CKS team are invited to comment on draft CKS topics. Individuals and organizations can also register an interest to feedback on a specific topic, or topics in a particular clinical area, through the Getting involved section of the Clarity Informatics website.
• Stakeholders identified from the following groups are invited to review draft topics:
  • Experts in the topic area.
  • Professional organizations and societies (for example, Royal Colleges).
  • Patient organizations, Clarity has established close links with groups such as Age UK and the Alzheimer’s Society specifically for their input into new topic development, review of current topic content and advice on relevant areas of expert knowledge.
  • Guideline development groups where the topic is an implementation of a guideline.
  • The British National Formulary team.
  • The editorial team that develop MeReC Publications.
• Reviewers are provided with clear instructions about what to review, what comments are particularly helpful, how to submit comments, and declaring interests.

Patient engagement

Clarity Informatics has enlisted the support and involvement of patients and lay persons at all stages in the process of creating the content which include:

• Topic selection
• Scoping of topic
• Selection of clinical scenarios
• First draft internal review
• Second draft internal review
• External review
• Final draft and pre-publication

Our lay and patient involvement includes membership on the editorial steering group, contacting expert patient groups, organizations and individuals.

Evidence exclusion criteria

Our policy

Scoping a literature search, and reviewing the evidence for CKS is a methodical and systematic process that is carried out by the lead clinical author for each topic. Relevant evidence is gathered in order that the clinical author can make fully informed decisions and recommendations. It is important to note that some evidence may be excluded for a variety of reasons. These reasons may be applied across all CKS topics or may be specific to a given topic.

Studies identified during literature searches are reviewed to identify the most appropriate information to author a CKS topic, ensuring any recommendations are based on the best evidence. We use the principles of the GRADE and PICOT approaches to assess the quality of published research. We use the principles of AGREE II to assess the quality of published guidelines.

Standard exclusions for scoping literature:

• Animal studies
• Original research is not written in English

Possible exclusions for reviewed literature:

• Sample size too small or study underpowered
• Bias evident or promotional literature
• Population not relevant
• Intervention/treatment not relevant
• Outcomes not relevant
• Outcomes have no clear evidence of clinical effectiveness
• Setting not relevant
• Not relevant to UK
• Incorrect study type
• Review article
• Duplicate reference

Organizational, behavioural and financial barriers

Our policy

The CKS literature searches take into consideration the following concepts, which are discussed at the initial scoping of the topic.

• Feasibility
  • Studies are selected depending on whether the intervention under investigation is available in the NHS and can be practically and safely undertaken in primary care.
• Organizational and Financial Impact Analysis
• Studies are selected and evaluated on whether the intervention under investigations may have an impact on local clinical service provision or national impact on cost for the NHS. The principles of clinical budget impact analysis are adhered to, evaluated and recorded by the author. The following factors are considered when making this assessment and analysis.
  • Eligible population
  • Current interventions
  • Likely uptake of new intervention or recommendation
  • Cost of the current or new intervention mix
  • Impact on other costs
  • Condition-related costs
  • In-direct costs and service impacts
  • Time dependencies
• Cost-effectiveness or cost-benefit analysis studies are identified where available. 

We also evaluate and include evidence from NICE accredited sources which provide economic evaluations of recommendations, such as NICE guidelines. When a recommended action may not be possible because of resource constraints, this is explicitly indicated to healthcare professionals by the wording of the CKS recommendation.

Declarations of interest

Our policy

Clarity Informatics requests that all those involved in the writing and reviewing of topics, and those involved in the external review process to declare any competing interests. Signed copies are securely held by Clarity Informatics and are available on request with the permission of the individual. A copy of the declaration of interest form which participants are asked to complete annually is also available on request. A brief outline of the declarations of interest policy is described here and full details of the policy is available on the Clarity Informatics website. Declarations of interests of the authors are not routinely published, however competing interests of all those involved in the topic update or development are listed below. Competing interests include:

• Personal financial interests
• Personal family interest
• Personal non-financial interest
• Non-personal financial gain or benefit

Although particular attention is given to interests that could result in financial gains or losses for the individual, competing interests may also arise from academic competition or for political, personal, religious, and reputational reasons. An individual is not obliged to seek out knowledge of work done for, or on behalf of, the healthcare industry within the departments for which they are responsible if they would not normally expect to be informed.

Who should declare competing interests?

Any individual (or organization) involved in developing, reviewing, or commenting on clinical content, particularly the recommendations should declare competing interests. This includes the authoring team members, expert advisers, external reviewers of draft topics, individuals providing feedback on published topics, and Editorial Steering Group members. Declarations of interest are completed annually for authoring team and editorial steering group members, and are completed at the start of the topic update and development process for external stakeholders.

Competing interests declared for this topic:

None.