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January 9, 1978

Entrapment Neuropathy From Baker's Cyst

Author Affiliations

From the Department of Neurology, Straub Clinic, Honolulu.

JAMA. 1978;239(2):135. doi:10.1001/jama.1978.03280290055024

BAKER'S cysts occur when the gastrocnemius-semimembranous bursa communicates with the knee joint and an effusion leads to a popliteal cyst. Rheumatoid synovitis may produce bursal swelling, distension, and eventually a Baker's cyst. If the cyst ruptures, this causes extravasation of the fluid into the compartments of the calf and produces symptoms and signs mimicking thrombophlebitis. On the other hand, if the cyst enlarges without rupturing, pressure may be exerted on branches of the low sciatic nerve and produce a neuropathy. I report the cases of five patients, each with an entrapment neuropathy secondary to Baker's cysts.

Report of Cases  The five patients included three men and two women ranging in age from 51 to 66 years. Four patients had classical rheumatoid arthritis, while foot-drop developed in one man after trauma to the knee. In all five patients, a painful palpable enlargement in the popliteal area became most symptomatic with the