A ganglion cyst is a fluid-filled cyst that usually forms at the wrist or elbow joint and arises from the tissue lining the tendons and joints. The cyst is painless and benign and contains a clear, jelly like fluid. It may increase in size slowly. Though the cyst can occur at any age, it is most common during the 30's and in old age. It is also more common in women than in men.