A ganglion is a benign (non-cancerous) cyst that forms around the joints or tendons.
Ganglion cysts usually appear on the back of the wrist. They look and feel like a smooth soft lump under the skin. They are made up of a thick jelly-like fluid, called synovial fluid, that surrounds joints and tendons to lubricate and cushion them during movement.
Ganglions can occur alongside any joint in the body but are most common around the wrist, hands and fingers.
It is not certain why ganglions form but they can be related to the ageing process or to injury to the joint or tendon. They occur when the synovial fluid that surrounds a joint or tendon collects and forms a swelling beneath the skin.
Ganglions are harmless but can vary in size and may cause mild pain, especially if they lie next to a nerve. If they do not cause any pain or discomfort they can be left and may disappear without treatment.
If a ganglion is particularly big or is causing pain, it can be removed by draining out the fluid with a needle or syringe (a procedure known as aspiration) or by surgery.
