A ganglion is a noncancerous, fluid-filled cyst that commonly forms near joints or tendons, often in the wrist or hand, but it can appear in other areas, such as the feet or ankles. These cysts are typically round or oval and can vary in size. Ganglions are filled with a thick, sticky fluid similar to the fluid that lubricates joints and tendons. While they are usually painless, they can sometimes cause discomfort, especially if they press on nearby nerves or restrict joint movement. The exact cause of ganglion cysts is unclear, but they are believed to form when there is a leakage of joint or tendon fluid into the surrounding tissue. Certain factors, such as repetitive motion or injury, may increase the risk. In most cases, ganglion cysts do not require treatment unless they cause pain or functional problems.

Treatment options include aspiration (draining the fluid) or surgical removal in more persistent cases.