Ganglions (sometimes called ganglion cysts) are common lumps that appear on the fingers, hand or wrist. They are herniation of the lubricating fluid in the joint or around the tendons, through a small defect that acts as a one way valve. The fluid then becomes thick and gelatinous (mucoid degeneration) as the lump enlarges.
Ganglions are usually not painful but as they enlarge they may start to stretch nerves or tendons, distort the nail and cause discomfort/concern. They may also become quite unsightly. Ganglions may rupture spontaneously and shrink/disappear for a while before re-appearing again. This is the source of the old fashioned treatment “hitting it with the Bible” treatment for ganglion cysts!
They typically occur around the back of the wrist (70%), the front of the wrist (15%), the end joint of the fingers/thumb (10%) or the base of the fingers (<10%).