A ganglion cyst is a collection of fluid around either a joint or tendon. A tendon, which attaches a muscle to bone, has an outer covering called a tendon sheath. Between the tendon and the tendon sheath is fluid which acts to lubricate the tendon and reduce friction as the tendon moves within the sheath.

Likewise, a joint, where two bones touch one another, has a balloon (joint capsule) around the outside of these bones. Within this balloon is fluid (synovial fluid) which also acts to lubricate and ease motion of the joint.

A traumatic event, either recognized or unnoticed, can cause the tendon sheath or joint capsule to herniate or balloon outward, called a ganglion cyst. This herniated area fills with fluid, frequently causing an enlarged, painful mass. Frequently, the mass will increase and decrease in size, varied by the amount of fluid in the cyst. Ganglion cysts can occur around any tendon or joint. Treatment options include either injecting the cyst with a steriod to reduce its size, draining the fluid of the cyst by insertion of a needle (which usually results in a quick return of the cyst), or surgical excision.

Additional information