A ganglion is a fluid-filled swelling of the lining of a joint or tendon. Although ganglions can form on any part of the foot, they most often appear on the ankle or top of the foot.
Ganglions tend to change in size, and are usually slow-growing.
Causes Repeated irritation can weaken the lining of a joint or tendon and lead to ganglions. People who wear boots are more vulnerable to ganglions, as this type of footwear puts stress on the foot and ankle. Symptoms Ganglions often form with no symptoms. However, if the ganglion puts pressure on the nerves in the overlying skin, it can cause tingling, numbness, or pain. Ganglions sometimes swell, and their size can change with different activities or a change in weather.