Baker cyst rupture — SCE Rheumatology MCQ

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EasyOsteoarthritis and Soft Tissue RheumatologyBaker cyst ruptureSCE Rheumatology

A 64-year-old man with knee osteoarthritis develops acute calf pain and swelling. Doppler ultrasound shows no DVT but fluid tracking down the intermuscular planes from the popliteal fossa. The knee has a small effusion and no fever. What is the most likely diagnosis?

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Correct answer: B — Ruptured Baker cyst

Explanation lettering: B = shown as A · E = shown as B · A = shown as D · D = shown as E

Ruptured Baker cyst is best because fluid tracking from the popliteal fossa with negative DVT imaging suggests ruptured Baker cyst. A is less suitable because necrotising fasciitis causes severe systemic toxicity and soft-tissue gas or rapid progression; B is less suitable because Achilles rupture causes weakness of plantarflexion and positive Thompson test; C is less suitable because DVT is a key mimic but Doppler is negative; D is less suitable because cellulitis would have skin infection features. Clinical pearl: ruptured Baker cyst is a classic pseudothrombophlebitis presentation.

Reference: Oxford Textbook of Rheumatology