Mucous cyst is a term given to a ganglion cyst when it occurs overlying the last joint of the finger. The last joint of the finger is medically termed the distal interphalangeal joint (DIP) joint. Wear and tear arthritis, known as osteoarthritis can oftentimes affect this joint. Bumps can occur in this joint from the arthritis itself and it can often be felt as a bony enlargement.
On the other hand, a mucous cyst occurs when the arthritis irritates the joint and skin and forms a fluid-filled cyst. These are oftentimes bluish in coloration; sometimes, the overlying skin gets thin. The fluid within the cyst is joint fluid analogous to a ganglion cyst (ganglion).
The danger occurs if they rupture. Similarly I have seen patients picking at them with needles and they could become secondarily infected. Because the cyst is in continuity to the underlying joint, infections can extend to the joint or bone. Therefore, it is important not to pick these areas and if the skin breaks to call immediately.
Treatment option includes splinting, injections, or surgical removal. When the skin does become very thin, surgery is oftentimes recommended to try to get the area closed before an infection occurs. Recent studies confirmed by my experience show a relatively high success rate of cortisone.
It is not uncommon for the nail to develop some ridging within it and since the cyst irritates the tissue from which the nail grows.
Many times, the cysts will diminish on their own. My belief is that the cyst is caused by irritation from the bone spur to the skin causing the fluid production. If it comes to surgery, you cannot only remove the cyst, this has leads to a high recurrence rate. The important aspect of surgery is to remove any underlying bone spurs causing the irritation.
If surgery is the choice you make, I perform it on an outpatient basis under a local anesthetic. The anesthesiologist is there to give you sedation if you want. The surgery generally involves a semicircular incision that gives me access to the cyst and joint. If the skin is thin, this incision allows me to move tissue around to gain coverage. After surgery the finger is splinted for a few weeks; the therapist will guide you through the early motion program. If you move it too soon, the skin over the joint will breakdown; the splinting and slow return of motion is to allow the skin to heal.
At the 3-5 week range the skin will often look quite red and angry looking. Since there is little fat and no muscle between the skin and bone, the area does become more inflamed than some at peak reaction. If you have any concerns about the wound call immediately.