Ganglion cysts are small cystic swellings around the tendons or joints, most often found in hand, foot, or knee. They are also known as "bible cysts" because the treatment in the past was to hit the cyst with a bible or large book to cause it to rupture.
Ganglion cysts are most common in the hand, more notably the wrist or fingers. They are often on the back of the hand. It is also common to have swelling at the metacarpophalangeal joint (where the finger meets the hand) and interphalangeal joint (the next joint out from there).
There are various causes of ganglion cysts, but the most common reason is a protruding area due to a weakened portion of a tendon sheath or joint capsule.
The most common treatment for ganglion cysts is surgery. A surgeon will aspirate (drain) the cyst and inject the area with corticosteroid. Stiffness and scar formation can occur from the surgery.