<Tr> <Td_colspan="2"> (edit on Wikidata) </Td> </Tr> <P> A Baker's cyst, also known as a popliteal cyst, is a benign swelling of the semimembranosus or more rarely some other synovial bursa found behind the knee joint . It is named after the surgeon who first described it, William Morrant Baker (1838--1896). It is not a "true" cyst, as an open communication with the synovial sac is often maintained . </P> <P> In adults, Baker's cysts usually arise from almost any form of knee arthritis (e.g., rheumatoid arthritis) or cartilage (particularly a meniscus) tear . Baker's cysts in children do not point to underlying joint disease . Baker's cysts arise between the tendons of the medial head of the gastrocnemius and the semimembranosus muscles . They are posterior to the medial femoral condyle . </P> <P> The synovial sac of the knee joint can, under certain circumstances, produce a posterior bulge, into the popliteal space, the space behind the knee . When this bulge becomes large enough, it becomes palpable and cystic . Most Baker's cysts maintain this direct communication with the synovial cavity of the knee, but sometimes, the new cyst pinches off . A Baker's cyst can rupture and produce acute pain behind the knee and in the calf and swelling of the calf muscles . </P>

Where does a baker's cyst come from