A ganglion is a small sac (cyst) filled with clear, jellylike fluid
that often appears as a bump on the hands and wrists, but it can also develop on
feet, ankles, knees, or shoulders. Ganglions are not cancerous.
The cause of ganglions is not known, but it may be a reaction to an
injury that causes the tendon sheath (which covers the tendon) or joint capsule
(which protects the joint) to form extra fluid and balloon out.
A ganglion grows out of a joint, pushing up out of the joint tissue
like a balloon. Most people with ganglions notice that the bumps appear
suddenly. They may be as small as a small green pea or larger, are usually not
painful, and may be movable. They may grow as activity increases, because more
fluid collects in the sac. They may also shrink and may break open on their
Ganglions are not serious and may go away on their own. If a
ganglion is not bothersome, treatment is usually not needed. If a ganglion is
painful or unsightly or limits activity, it can be drained (aspirated) and
possibly injected with a corticosteroid, although ganglions often come back
after being drained. A ganglion can also be surgically removed.
Smashing a ganglion with a heavy object is not recommended because
it usually does not work and may cause injury.