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Bakers Cyst

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Other Names

  • Popliteal synovial cyst
  • Ganglion cyst of the knee
  • Synovial cyst of the knee
  • Baker's Cyst
  • Parameniscal cyst
  • Perimeniscal cyst
  • Meniscal cyst
  • Pseudothrombophlebitis Syndrome
  • Primary popliteal cyst


  • This page refers to a synovial or ganglion cyst of the knee, which when presenting posteriorly is referred to as a Baker's Cyst (BC)


  • Named after British surgeon William Morant Baker’s case series published in 1877[1]
  • First described by Robert Adams in 1840[2], and subsequently by Foucher in 1856[3]
  • Further characterized by Wilson in 1938 who dissected 30 knees, of which 58% had a direct connection with the knee joint[4]


  • Found on 38% of knee MRIs on symptomatic patients[5]
  • Found in 40-54% of adult knees based on cadaveric studies[6]
  • Most commonly seen in adults between ages 35 and 70 (need citation)
  • Pediatric
    • Among children, most frequently seen between ages 4 and 7, reported in children as young as 2[7]
    • In pediatric knee MRI, prevalence estimated at 6.3%[8]


  • Communication
    • Occurs within a bursa between the Semimembranosus (SemiM) and medial head of the Gastrocnemius (Gastroc)
    • Joint-cyst communication considered to function like a 1-way valve
  • 1 way valve[9]
    • Allows synovial fluid to pass into bursa where it is sequestered
    • In flexion, valve is open allowing flow
    • In extension, valve is closed due to muscle tension of SemiM and Gastroc
  • Function
    • May provide protective effect against hydraulic pressure from knee effusions
    • Size of BC roughly correlates with size of knee effusion[10]
  • Histology
    • Cyst walls resemble synovial tissue with fibrosis suggesting chronic nonspecific inflammation[11]
    • Cyst fluid is often thickened by the presence of fibrin
    • Rauschnig et al found no difference in histopathology between symptomatic and asymptomatic knees
  • Pediatric considerations
    • Majority have no communication with the joint capsule and may arise spontaneously[12]
    • When they do communicate with the joint, resemble those seen in adults


  • Cyst Anatomy
    • Bursal communication between the Semimembranosus (SemiM) and medial head of the Gastrocnemius (Gastroc)
    • There may be occasional involvement of the subgastrocnemius bursa[13]
    • Case report of synvial cyst herniating out laterally through the Iliotibial Band[14]

Associated Pathology

Risk Factors

Differential Diagnosis

Clinical Features

  • History
    • Patients may report insidious, posterior knee pain
    • Additionally fullness, achiness, mass, and stiffness
    • The most common symptoms are swelling (76%), posterior aching (32%)[18]
    • Pain with full or terminal knee extension
    • Often have symptoms consistent with meniscal or chondral injuries
  • Physical Exam: Physical Exam Knee
    • Findings often consistent with meniscal or chondral injuries
    • With large cysts, posteromedial fullness may be present but many smaller cysts are not palpable
  • Special Tests
    • Foucher Sign: Examine posterior mass in full knee extension and flexion, should be soft in flexion
    • Homan Sign: Extend knee, passively dorsiflex ankle and squeeze calf


Bakers Cyst ultrasound long axis
Bakers Cyst ultrasound short axis


  • Standard Knee Radiographs
    • Screening tool
    • Not typically useful for evaluating a bakers cyst
  • Can detect other pathology associated with bakers cyst
    • E.g.: Osteoarthritis, Gout, Osteochondral Defect
    • Loose bodies may be seen within the bakers cyst
  • Arthrography
    • Previously gold standard for evaluation[19]
    • Has fallen out of favor for MRI, US


  • Advantages
    • Cheap, lacks radiation, ease of use
  • Disadvantages
    • User dependent, cant evaluate all soft tissue injuries
  • Findings
    • Anechoic or hypoechoic, circumferential structure
    • Lacks flow and doppler signal of vascular structures
  • Accuracy[20]
    • Sensitivity: 100%
    • Specificity: 100%
    • PPV: 100%
    • NPV: 100%
    • Accuracy: 100%


  • Gold standard for evaluating BC and other soft tissue structures
  • Findings
    • Appear as a water-intensity fluid collection (low signal intensity on T1, high signal intensity on T2-weighted images)[16]
  • Description
    • Most are small, unilocular but can also be septated or multiloculated
    • Size, sites of extension, rupture can change appearance of fluid collection
    • Loose bodies/debris can be present


  • No specific classification
  • Important to characterize
    • Communicating vs noncommunicating
    • Loculated, multiloculated or septated
    • Underlying etiology



  • General
    • Initial treatment of choice unless complications
    • Important to target the underlying disorder
  • Physical Therapy
    • Maintain range of motion and knee flexibility
  • Intra-articular Corticosteroid Injection
    • Intra-articular has been found to decrease size, symptoms of cyst[21]
  • Ultrasound-guided posterior cyst aspiration and Corticosteroid Injection
    • This is particularly valuable in the uncommon noncommunicating, multiloculated or septated cyst


  • Indications
    • Failure of conservative therapy
    • Complicated including infection, neurovascular insult
  • Technique
    • Arthroscopic debridement
    • Arthroscopic cyst decompression or excision
    • Less commonly, open cyst excision
    • Correction of intra-articular pathology

Rehab and Return to Play


  • There are no specific bakers cyst rehabilitation guidelines
  • Important to maintain full knee flexion and range of motion

Return to Play

  • There are no clear return to play guidelines

Complications and Prognosis


  • Surgical
    • Response to surgical excision seems to correlate with ability to correct intra-articular pathology
    • Rauschning et al: 46 surgical excisions, 63% recurred, 33% had wound complications or pseudothrombophlebitis after[22]
    • Rupp et al: Arthroscopic treatment for 16 intra-articular disorders, 11 cysts persisted of which 2 became larger at 1 year postop[23]
      • Chondral lesions appeared to be most important prognostic factor, all patients had outerbridge III or IV lesions


See Also



  1. Baker WM. On the formation of synovial cysts in the leg in connection with disease of the knee joint. 1877. Clin Orthop Relat Res. 1994;299:2-10.
  2. Adams R. Chronic rheumatic arthritis of the knee joint. Dublin J Med Sci. 1840;17:520-522.
  3. Foucher E. Memoire sur les kystes de la region poplitee. Arch Gen Med. 1856;2:313.
  4. Wilson PD, Eyre-Brook AL, Francis JD. A clinical and anatomical study of the semimembranosus bursa in relation to popliteal cyst. J Bone Joint Surg Am. 1938;20:963-984.
  5. 5.0 5.1 Sansone V, De Ponti A, Minio Paluello G, Del Maschio A. Popliteal cysts and associated disorders of the knee: critical review with MR imaging. Int Orthop. 1995;19:275-279.
  6. Taylor AR, Rana NA. A valve: an explanation of the formation of popliteal cysts. Ann Rheum Dis. 1973;32:419-421
  7. GRISTINA, ANTHONY G., and PHILIP D. WILSON. "Popliteal cysts in adults and children: a review of 90 cases." Archives of Surgery 88.3 (1964): 357-363.
  8. De Maeseneer, Michel, et al. "Popliteal cysts in children: prevalence, appearance and associated findings at MR imaging." Pediatric radiology 29.8 (1999): 605-609.
  9. Rauschning W. Anatomy and function of the communication between the knee joint and popliteal bursae. Ann Rheum Dis. 1980;39:354-358.
  10. Hill CL, Gale DG, Chaisson CE, et al. Knee effusions, popliteal cysts, and synovial thickening: association with knee pain in osteoarthritis. J Rheumatol. 2001;28:1330-1337.
  11. Rauschning W, Fredriksson BA, Wilander E. Histomorphology of idiopathic and symptomatic popliteal cysts. Clin Orthop Relat Res. 1982;164:306-311.
  12. Akagi, Ryuichiro, et al. "Natural history of popliteal cysts in the pediatric population." Journal of Pediatric Orthopaedics 33.3 (2013): 262-268.
  13. Akagi, Ryuichiro, et al. "Natural history of popliteal cysts in the pediatric population." Journal of Pediatric Orthopaedics 33.3 (2013): 262-268.
  14. Jensen KH, Jorgensen U. Lateral presentation of a Baker’s cyst. Clin Orthop Relat Res. 1993;287:202-203
  15. Tarhan S, Unlu Z. Magnetic resonance imaging and ultrasonographic evaluation of the patients with knee osteoarthritis: a comparative study. Clin Rheumatol. 2003;22:181-188.
  16. 16.0 16.1 Marti-Bonmati L, Molla E, Dosda R, Casillas C, Ferrer P. MR imaging of Baker cysts: prevalence and relation to internal derangements of the knee. MAGMA. 2000;10:205-210.
  17. Corten K, Vandenneucker H, Reynders P, Nijs S, Pittevils T, Bellemans J. A pyogenic, ruptured Baker’s cyst induced by arthroscopic pressure pump irrigation. Knee Surg Sports Traumatol Arthrosc. 2009;17:266-269
  18. Bryan RS, DiMichele JD, Ford GL., Jr. Popliteal cysts. Arthrography as an aid to diagnosis and treatment. Clin Orthop Relat Res. 1967;50:203-208.
  19. Torreggiani WC, Al-Ismail K, Munk PL, et al. The imaging spectrum of Baker’s (popliteal) cysts. Clin Radiol. 2002;57:681-691.
  20. Ward EE, Jacobson JA, Fessell DP, Hayes CW, van Holsbeeck M. Sonographic detection of Baker’s cysts: comparison with MR Imaging. AJR Am J Roentgenol. 2001;176:373-380.
  21. Acebes JC, Sanchez-Pernaute O, Diaz-Oca A, Herrero-Beaumont G. Ultrasonographic assessment of Baker’s cysts after intra-articular corticosteroid injection in knee osteoarthritis. J Clin Ultrasound. 2006;34:113-117
  22. Rauschning W, Lindgren PG. Popliteal cysts (Baker’s cysts) in adults: I. Clinical and roentgenological results of operative excision. Acta Orthop Scand. 1979;50:583-591
  23. Rupp S, Seil R, Jochum P, Kohn D. Popliteal cysts in adults: prevalence, associated intraarticular lesions, and results after arthroscopic treatment. Am J Sports Med. 2002;30:112-115.
  24. Eichinger JK, Bluman EM, Sides SD, Arrington ED. Surgical management of septic arthritis of the knee with a coexistent popliteal cyst. Arthroscopy. 2009;25:696-700.
  25. Ji JH, Shafi M, Kim WY, Park SH, Cheon JO. Compressive neuropathy of the tibial nerve and peroneal nerve by a Baker’s cyst: case report. Knee. 2007;14:249-252.
Created by:
John Kiel on 16 December 2020 21:18:39
Last edited:
26 January 2023 19:57:13