Ganglion cysts of the wrist and hand are fairly common. They are benign but can still cause problems. If they get large enough, pressure on the nerve can cause wrist and finger pain, numbness, and weakness.

Most ganglia are filled with a clear fluid that comes from the synovial fluid in the nearby wrist joints. If you hold a small flashlight up against the cyst, the light will shine right through it.

The cyst itself has an outer wall made up of collagen fibers put together in a random fashion. The ganglion may have more than one lobe, all filled with the same fluid. The cyst gets larger and smaller as the fluid moves in and out of the cyst.

If the lobes get sealed off, then the cyst stays the same size. But if the cyst has an opening into the joint, fluid from the joint can move back and forth between the two spaces.

Sometimes ganglion cysts go away or resolve by themselves. In other cases, they can be drained and they don't fill up again. Most often surgery is needed to remove the cyst and the stalk of tissue that's connecting it to the joint.