A 45-year-old man presented with gradually increasing swelling on the posterior aspect of the left knee since two years and increased discomfort in knee extension since two months
Ultrasonography of the left popliteal fossa reveals a well defined 4 x 2,5 x 3 cm sized cyst extending into the joint space along the medial aspect of left popliteal fossa between the semimembranosus tendon and medial head of gastrocnemius. The cyst has a narrow neck causing the "speech bubble" appearance. There are echogenic foci within the cyst.
A Baker's cyst is named after William Morrant Baker (1838–1896), a 19th-century British surgeon and lecturer at St. Bartholomew's Hospital in London. He first described the condition 1877.