What Causes a Ganglion Cyst?

A ganglion cyst is a round, firm sac of fluid that develops near the joints of the wrist or fingers, the top of the foot, or on the outside of the ankle and knee joints. People with osteoarthritis or those who have damaged their joints or tendons are more likely to develop ganglion cysts than the general population; the exact cause for this type of cyst is unknown. The cysts are non-cancerous and generally not painful, unless they are pressing on a nerve. Treatment involves draining the cyst, steroids, and splinting or surgical removal.

Women and those between 20-40 years old are more prone to develop these cysts. A person can develop one large ganglion cyst or several smaller ones. The cyst, or group of cysts, grows on a stalk that emerges from a joint. They are usually painless and benign.

The actual cause of a ganglion cyst is unknown. Doctors do know that a cyst may grow larger or smaller over time. Increased use may be related to cyst growth. This growth may cause the cyst to press on a nerve and cause pain. Rest or immobilization of the joint usually leads to a decrease in the size of the cyst.

Those with osteoarthritis, or arthritis due to wear and tear, and people who have injured their joints or tendons tend to develop ganglion cysts more often. Fluid build up caused by arthritis may leak out into the tendon, causing a new cyst or filling up an already existing one. The fluid inside of a ganglion cyst is similar to the fluid found within the joints or around tendons.

Treatment of this medical condition varies. If a ganglion cyst is not painful, the doctor may prefer merely to monitor it. Some people dislike the way the cyst looks or may have pain associated with it. In these cases, treatment may entail draining the fluid or surgery.

To aspirate, or drain, a ganglion cyst, the doctor injects a local anesthetic. Using a needle, the fluid is then removed. Once the fluid is gone, the patient may receive a steroid injection into the cyst. After the procedure is complete, the joint is usually immobilized. The cyst will eventually refill with fluid in 60% of cases following drainage.

Surgery may be recommended in some instances. Possible surgical risks include damage to the surrounding tissues. The operation is done on an outpatient basis in the doctor's office under local anesthesia. Post-operative pain may be treated with over-the-counter analgesics, such as ibuprofen. Although the cyst may return after surgery, the likelihood is much less when treated with aspiration.