Baker's cyst is characterized by a sensation of bulging or tightness accompanied by pain behind the knee. The painful sensation worsens when the affected knee is moved or fully extended. Baker's cyst is also alternatively known as popliteal cyst.

A baker's cyst is a relatively simple cyst which can be detected with an ultrasound or a magnetic resonance imaging or MRI scan.

In most cases, baker's cyst will disappear on its own and require no further treatment. However, in cases where the cyst is large and painful, a physician may drain the fluid from the knee joint using a needle with the help of ultrasound guidance. Physical therapy may also be recommended to preserve knee function. In addition, corticosteroid medications may be advised for pain relief.

Baker's cyst manifests with a distinctive bulging or swelling behind the knee and sometimes in the leg, intense knee pain, and stiffness in the affected limb.

Baker's cysts usually develop as a consequence of related problems in the knee joint, such as a cartilage tear or arthritis. Both of these conditions can cause the knee to overproduce synovial fluids, which can accumulate abnormally to form a Baker's cyst. Synovial fluids can be likened to the oil that lubricates a door hinge to reduce friction between its components as well as to minimize wear and tear. Synovial fluids are those that help the legs swing and move smoothly with minimal friction in the parts of the knees. However, if too much synovial fluid is produced, the popliteal bursa (or the tissue pouches through which the fluid circulates) fills with fluid and expands. The resulting bulge is called baker's cyst.

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