Mucous cysts are small, fluid-filled sacs that form on the fingers. They are associated with osteoarthritis (OA) and usually develop in patients 50 to 70 years old. These cysts appear between the last joint of the finger and the bottom of the fingernail. Unless a mucous cyst is painful or in danger of rupturing, it can be left alone without causing harm to the patient. But even surgically removing a mucous cyst may not alleviate pain if the underlying cause of the pain is old age.
A mucous cyst is typically visible just under the skin on the finger. It may be painful. You may notice a groove in the fingernail just above the cyst. The groove is a result of pressure from the cyst on the nailbed. The skin over the cyst may have thinned.
Your doctor will ask for a history of the problem and examine your fingers. Your doctor may also order an X-ray. An X-ray of the DIP joint may show degeneration related to old age, including bone spurs, joint space narrowing, and hardening of the subchondral bone, the layer of bone just below the articular cartilage in the joint. A patient may also have Heberden’s nodes. These are simply the bumps formed by bones spurs arising from the finger joint due to the old age.
Treatment for mucous cysts may be either nonsurgical or surgical. The relative risks and benefits of any mucous cyst treatment should be considered carefully.
Observation is often sufficient treatment for mucous cysts. Mucous cysts are not typically harmful and usually do not grow worse without treatment.
However, sometimes a mucous cyst will rupture. When this occurs, it creates a path directly into the joint where bacteria could enter and cause a serious infection inside the joint. When this happens, antibiotics are applied directly to the site and the finger is wrapped in a dressing. Oral antibiotics are also prescribed. If the joint develops an infection despite these steps, surgery is required. During surgery, the area, including the DIP joint, is carefully cleaned, and a dressing is applied.
Surgery is recommended if you feel significant pain or if the cyst and skin appear ready to rupture.
Needle puncture is one option. In this procedure, the cyst is punctured and aspirated. (Aspiration means drawing the fluid out with suction.) However, this procedure has less than a 50 percent success rate.
Another option involves excision (removal) of the cyst and its connection to the DIP joint. Patients should be aware that removing a mucous cyst may not eliminate pain if the pain is from the underlying OA. In this procedure, the cyst, stalk, and any bone spurs on the DIP joint are removed. If the skin on the finger is too closely attached to the cyst, a bit of the skin may need to be removed from the finger. If that’s the case, a small skin graft is added to the spot. Surgery can usually be performed using regional anesthesia, meaning only the arm or finger is numbed with lidocaine.
Complications may occur with both procedures. A slight risk of infection exists with both. Even after an excision surgery, a mucous cyst may reappear, though this is rare.