No one knows exactly what causes a ganglion cyst to develop. It grows out of a joint or the lining of a tendon, looking like a tiny water balloon on a stalk, and seems to occur when the tissue that surrounds a joint or a tendon bulges out of place. Inside the cyst is a thick lubricating fluid similar to that found in joints or around tendons.
Factors that may increase your risk of ganglion cysts include:
- Your sex and age. Ganglion cysts can develop in anyone, but they most commonly occur in women between the ages of 20 and 40.
- Osteoarthritis. People who have wear-and-tear arthritis in the finger joints closest to their fingernails are at higher risk of developing ganglion cysts near those joints.
- Joint or tendon injury. Joints or tendons that have been injured in the past are more likely to develop ganglion cysts.