Summary
Definition
Popliteal cyst (also known as Baker's cyst) is the result of an accumulation of joint synovial fluid outside the knee joint; it forms behind the knee in the interval between the semimembranosus and the medial gastrocnemius. This occurs via increased intrasynovial pressure, and causes the synovial capsule to bulge at an area where there is a lack of external anatomical support.[1] The most common underlying conditions that lead to overproduction of synovial fluid include arthritis and meniscal tears. [Figure caption and citation for the preceding image starts]: Popliteal cystCreated by BMJ Publishing Group [Citation ends].
History and exam
Key diagnostic factors
- presence of risk factors
- popliteal bulge
- knee pain
- leg swelling
- calf tenderness
Other diagnostic factors
- calf ecchymosis
- lyme disease
Risk factors
- knee joint trauma
- underlying knee joint arthritis or synovitis
- underlying knee joint infection
- increasing age
Diagnostic investigations
1st investigations to order
- duplex ultrasound of the leg
Investigations to consider
- MRI of the leg
- CT scan of the leg
Treatment algorithm
asymptomatic
symptomatic: initial treatment
symptomatic: refractory to initial conservative treatment
Contributors
Authors
John D. Kelly IV, MD
Professor of Clinical Orthopaedic Surgery
Director of Sports Shoulder Service
Orthopaedic Surgery
University of Pennsylvania
Philadelphia
PA
Disclosures
JK declares that he has no competing interests.
Acknowledgements
Dr John D. Kelly IV would like to gratefully acknowledge Dr Antonios P. Gasparis and Dr Nicos Labropoulos, previous contributors to this topic.
Disclosures
APG declares that he has no competing interests. NL is the author of multiple references cited in this topic.
Peer reviewers
Brian Sabb, DO
Clinical Lecturer II
Orthopedic Radiologist
Department of Radiology
University of Michigan Medical Center
Ann Arbor
MI
Disclosures
BS declares that he has no competing interests.
Hill Gaston, MA, PhD, BM BCh, FRCP, FMedSci
Professor of Rheumatology
University of Cambridge
Clinical Director
West Anglia CLRN
Cambridge
UK
Disclosures
HG declares that he has no competing interests.
Richard Wakefield, BM, MRCP, MD
Senior Lecturer in Rheumatology
Academic Section of Musculoskeletal Disease
Leeds Institute of Molecular Medicine
Chapel Allerton Hospital
Leeds
UK
Disclosures
RW declares that he has no competing interests.
Differentials
- Deep vein thrombosis (DVT)
- Popliteal haematoma
- Popliteal muscle tear
More Differentials
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