Baker's cyst
（重定向自Baker cyst）
![](/Images/godic/202412/23/Valvular_mechanism_of_Baker_cyst0821.png")
![Baker's cyst (popliteal cyst) is located behind the knee and is a swelling of the popliteal bursa. In this image, the Baker's cyst is the yellowish bulbous tissue which was identified during routine dissection.](/Images/godic/202412/23/Bakers_cyst0821.jpg")
![Baker's cyst on axial MRI with communicating channel between the semimebranosus muscle and the medial head of the gastrocnemius muscle.](/Images/godic/202412/23/Bakerzyste_MRT_ax0821.jpg")
![Baker's cyst on MRI, sagittal image.](/Images/godic/202412/23/Bakerzyste1_MRT_sag0821.jpg")
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). This is not a "true" cyst, as an open communication with the synovial sac is often maintained.