Popliteal (Baker) Cyst
- A fluid-filled synovial sac arising in the popliteal fossa as a distention of (typically) the gastrocnemial-semimembranous bursa; not a true cyst
- Can be unilateral or bilateral
- Most frequent cystic mass around the knee
- Primary cysts are a distention of the bursa (arise independently without an intra-articular disorder).
- Secondary cysts occur if there is a communication between the bursa and knee joint, allowing articular fluid to fill the cyst.
- Associated with synovial inflammation
- Bimodal distribution
- Children ages 4 to 7 years
- Adults increasing with age
- Primary cysts usually seen in children <15 years
- Secondary cysts seen in adults
- Variable adult prevalence of 19–47% in symptomatic knees and 2–5% in asymptomatic knees
- In children: 6.3% in symptomatic knees; 2.4% in asymptomatic knees
Etiology and Pathophysiology
Associated intra-articular pathology includes
- Meniscal tears, mostly of the posterior horn
- Anterior cruciate ligament (ACL) insufficiency
- Degenerative articular cartilage lesions
- Rheumatoid arthritis (20%)
- Osteoarthritis (50%)
- Gout (14%)
- Other potential factors
- Infectious arthritis
- Villonodular synovitis
- Connective tissue diseases
- Extension or herniation of synovial membrane of the knee joint capsule or connection of normal bursa with the joint capsule
- May result from increased intra-articular pressure
- Commonly seen with knee effusions
- Direct trauma to the bursa is likely the primary cause in children because of no communication between the bursa and the joint.
- A valve-like mechanism allowing one-way passage of fluid from the joint to the bursal connection has been described.
- Osteoarthritis of knee (most common)
- Rheumatoid arthritis
- Meniscal degeneration or tear
- Advancing age
- Ligamentous trauma
- Ligamentous insufficiency
Commonly Associated Conditions
Any condition causing knee joint effusion
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Domino, Frank J., et al., editors. "Popliteal (Baker) Cyst." 5-Minute Clinical Consult, 27th ed., Wolters Kluwer, 2020. Medicine Central, im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/1688688/all/Popliteal__Baker__Cyst.
Popliteal (Baker) Cyst. In: Domino FJF, Baldor RAR, Golding JJ, et al, eds. 5-Minute Clinical Consult. Wolters Kluwer; 2020. https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/1688688/all/Popliteal__Baker__Cyst. Accessed May 29, 2023.
Popliteal (Baker) Cyst. (2020). In Domino, F. J., Baldor, R. A., Golding, J., & Stephens, M. B. (Eds.), 5-Minute Clinical Consult (27th ed.). Wolters Kluwer. https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/1688688/all/Popliteal__Baker__Cyst
Popliteal (Baker) Cyst [Internet]. In: Domino FJF, Baldor RAR, Golding JJ, Stephens MBM, editors. 5-Minute Clinical Consult. Wolters Kluwer; 2020. [cited 2023 May 29]. Available from: https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/1688688/all/Popliteal__Baker__Cyst.
* Article titles in AMA citation format should be in sentence-case
TY - ELEC T1 - Popliteal (Baker) Cyst ID - 1688688 ED - Domino,Frank J, ED - Baldor,Robert A, ED - Golding,Jeremy, ED - Stephens,Mark B, BT - 5-Minute Clinical Consult, Updating UR - https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/1688688/all/Popliteal__Baker__Cyst PB - Wolters Kluwer ET - 27 DB - Medicine Central DP - Unbound Medicine ER -