Mucous cysts are small, fluid-filled sacs that form on the fingers and usually develop in patients 50 to 70 years of age. The mucous cyst usually appears at the joint nearest to the fingernail, called the distal interphalangeal (DIP) joint, and can be found on the thumb or on any of the other fingers. It presents as a small, sometimes painful, nodule in the DIP joint area. Most patients who develop a mucous cyst have wear and tear arthritis or osteoarthritis of the involved joint.

What causes a Mucous Cyst?

As the mucous cyst grows, it will often have a clear appearance due to the nature of the fluid-like material in your joints called synovial fluid. The mucous cyst occurs due to “kissing” osteophytes or bone spurs in the area of the DIP joints. This is related to osteoarthritis frequently present in these joints. The “kissing” osteophytes or bone spurs puncture the capsule of the joint, causing clear fluid from the joint surface to leak into the surrounding tissues. The tissues then form a hard capsule known as a cyst around this fluid. The cyst typically grows towards the area of the nail fold where nail plate growth occurs. Frequently, a nail deformity will form in the region of the mucous cyst due to it pressing on the nail matrix. A mucous cyst can often be directly visualized in the region due to thinning of the skin.

Diagnosis

An Orthopaedic hand specialist will first ask for a history of the problem and examine the patient’s fingers. An X-ray of the finger may be required to show degeneration related to osteoarthritis in the DIP joint area. This includes bone spurs and joint space narrowing. A patient may also have Heberden’s nodes, which are the bumps formed by osteophytes or bones spurs arising from in the finger.

Treatment Options for Mucous Cysts

Treatment for mucous cysts may either be nonsurgical or surgical. Nonsurgical treatment for mucous cysts includes observation by an Orthopaedic hand specialist. However, sometimes a mucous cyst will rupture. When a rupture occurs, it creates a path directly from the skin into the joint where bacteria can enter and cause a serious infection. For this reason, a mucous cyst should never be punctured at home due to the risk of contamination or infection of the joint area. Surgery is recommended if the patient feels significant pain or if the cyst and skin appear ready to rupture.

Surgical treatment typically requires outpatient surgical reconstruction with an excision (removal) of the cyst. This procedure involves a trimming and smoothing of the “kissing” osteophytes or bone spurs, so the capsule may heal surrounding the joint. If the skin on the finger is too closely attached to the cyst, a small piece of the skin may need to be removed from the finger. In this situation, a small skin graft is necessary. Surgery can usually be performed using regional anesthesia, meaning only the finger is numbed with lidocaine. The surgery lasts approximately one-half hour and is done as an outpatient procedure. The procedure has a relatively straightforward postoperative course.

Rehabilitation for Mucous Cyst Surgery

If a mucous cyst is surgically removed, a patient’s hand therapist will make a splint for the end of the
finger. The patient will then progress through range-of-motion exercises over a two week period. Other than some soreness in the area of the finger with pinch or grasp activity, healing is relatively straightforward. The sutures are removed approximately 10 days after surgery and normal activities are usually resumed two to three weeks after surgery.

Complications are rare but could include infection or progressive arthritis which can require a fusion of the joint. The nail deformity frequently resolves gradually with the treatment of the mucous cyst.

Dr. Arthur M. Sharkey is Board Certified in General Surgery as well as Plastic and Reconstructive Surgery with additional qualifications in Hand Surgery. Dr. Sharkey attended medical school at the University of Illinois, where he also completed his residency in General Surgery. He completed his residency in Plastic Surgery at St. Louis University, followed by fellowship training in Hand Surgery at Christine M. Kleinert Institute for Hand and Microsurgery in Louisville, KY. Dr. Sharkey is an active member of the American Society for Plastic and Reconstructive Surgery.