Mucous Cyst

Mucous cysts are small fluid-filled sacs that form on the finger or thumb, typically near the base of the fingernail. The small, sometimes painful, cyst is connected to the joint capsule by a stalk that allows fluid to move into the cyst from the joint. Most mucous cysts develop slowly and are common in patients with arthritis or osteoarthritis in the joint.


Mucous cysts are most commonly associated with osteoarthritis in the joint where the cyst develops. The cysts are formed when connective tissue that attaches the tendons in the finger wears away. As this happens, collagen from the tissue left behind collects in a pool to form a cyst. Because this condition is mostly associated with arthritis, patients are primarily over age 50.


The mucous cyst is mostly found on the index finger of the dominant hand at the joint near the fingernail. The cyst is a small bump with clear fluid that forms a thick, firm to the touch, outer layer. Mucous cysts are often mistaken for a blister. Although most mucous cysts are not painful, they may rupture, resulting in the drainage of a clear, thick liquid. If this happens, there is risk for severe joint infection.


Although the mucous cyst often presents little or no pain, it is recommended that a doctor assess the condition and examine the patient for any other underlying issues. Since most mucous cysts are related to arthritis, a physician may order an x-ray to confirm the root cause and level of degeneration. In many cases, bone spurs have also formed on top of the joint near the cyst.


In most cases, the mucous cyst does not require treatment and should be monitored. Small cysts may be treated with needle puncture and steroid medication. In severe cases where there is risk of rupture, pain, or nail deformation, surgery may be recommended.

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