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 usually grow slowly.
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. Bone spurs (bony outgrowths) may also cause ganglions by irritating the joints and tendons.
Ganglions often form with no symptoms. But 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.
Because ganglions are sometimes mistaken for tumors, it’s important to have a complete examination and, possibly, tests to confirm the diagnosis.
If a bone spur is suspected, x-rays may be needed. Fluid removal (needle aspiration) may be done to help determine the degree of swelling and to decrease pain. To confirm a ganglion, magnetic resonance imaging (MRI) may be done, which reveals images of soft tissue and bone.
Ganglions are often difficult to treat without surgery-but nonsurgical methods may be helpful in relieving some of your symptoms.