What is a ganglion cyst on the back side of the finger?

A ganglion cyst on the back of the finger is a pocket of lubricating fluid from the underlying joint (figure). Another name for this is a mucous cyst. They are typically associated with underlying arthritis.^1,2,3

Ganglion cysts may look unusual, but they are harmless. ^1,2,3

Figure: a ganglion cyst.

Signs and symptoms

Ganglions can feel as hard as a bone. The underlying arthritis may cause pain, but the cysts do not. The cyst can be prominent. There may be a groove in the fingernail. If popped, the cyst may leak fluid. If it gets red, warm, and painful, it might be infected. This is uncommon. ^1,2,3

Evaluation

The diagnosis is usually clear on examination.³