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Morrant Baker (popliteal) cyst or pseudothrombophlebitis syndrome
A cyst in the midline of the popliteal fossa, at or below the femorotibial junction.
Epidemiology:
1) incidence is 5% (by MRI)
2) commonly associated with inflammatory joint disease, especially rheumatoid arthritis
Pathology:
1) popliteal cysts are connected to the gastrocnemio-semimembranous bursa in the calf
2) pressure diverticulum of the synovial sac protruding through the joint capsule of the knee
3) may compress the popliteal vessels
4) one-way valve effect where fluid may go from the knee to the popliteal synovial bursa, but not in reverse
5) cysts may dissect into the calf or rupture
Clinical manifestations:
1) calf pain & swelling
2) knee effusion
3) protrudes when the knee is extended & is not visible with flexion, unless very large
4) if the communication is patent, gradual steady pressure on the sac forces some fluid back into the joint cavity, temporarily reducing swelling
5) swelling may be translucent
6) cysts are usually along the medial side distal to the transverse skin crease
Radiology:
1) duplex ultrasound
a) assessment of popliteal space
b) rules in/out deep vein thrombosis (DVT)
2) magnetic resonance imaging
3) arthrography is gold standard for diagnosis
Differential diagnosis:
- deep vein thrombosis
Management:
1) no treatment necessary for asymptomatic popliteal cysts [2]
2) glucocorticoid injection
3) joint aspiration
4) ultrasound-guided cyst aspiration with glucocorticoid injection [5]
5) bed rest for 48 hours
6) elastic wrap when weight-bearing or ambulating to reduce swelling of calf & ankle
7) gradient elastic stocking as calf & ankle swelling diminish
8) non-steroidal anti-inflammatory agents for pain & inflammation
9) surgery
General
cyst
References
- DeGowin & DeGowin's Diagnostic Examination, 6th edition,
RL DeGowin (ed), McGraw Hill, NY 1994, pg 732
- Medical Knowledge Self Assessment Program (MKSAP) 11, 18.
American College of Physicians, Philadelphia 1998, 2018.
- Zhang WW, Lukan JK, Dryjski ML.
Nonoperative management of lower extremity claudication caused
by a Baker's cyst: case report and review of the literature.
Vascular. 2005 Jul-Aug;13(4):244-7.
PMID: 16229799
- Labropoulos N, Shifrin DA, Paxinos O.
New insights into the development of popliteal cysts.
Br J Surg. 2004 Oct;91(10):1313-8.
PMID: 15376180
- NEJM knowledge+ Rheumatology