What Are Mucous Cysts?
Mucous cysts are a type of small ganglion (fluid filled) cyst found near the end joint of an arthritic finger joint. The cyst is caused by a small bone spur that irritates the lining of the finger joint that causes an outpouching of this lining underneath the skin. They often start as a small firm bump, but may increase in size. As the cyst gets larger, it may rupture, leaking a clear fluid. There is usually little pain from the cysts themselves; however, discomfort can be from the underlying arthritis. In larger, long-standing cysts, the fingernail may develop a ridge deformity.
How Are Mucous Cysts Diagnosed?
The cyst is diagnosed by physical exam, as they have a typical appearance. X-rays are used to evaluate the joint for arthritis and identify the offending bone spur. Advanced imaging is rarely needed.
How Are Mucous Cysts Treated?
Most small cysts are treated with simple observation. It is not recommended to “pop” the cyst as this may lead to an infection of the finger joint. Surgery is reserved for cysts that are larger in size and at risk for rupture due to the thinning of the overlying skin.
Excision of the cyst is performed with a short outpatient procedure done under either local anesthesia or light sedation. It is important to remove the bone spur as well as the cyst to prevent recurrence. The finger is immobilized in a splint for approximately a week, after which the sutures are removed and return to normal activity follows over the next few weeks.