what is ganglion
A ganglion is a sac-like swelling or cyst formed from the tissue that lines a joint or tendon. The tissue, called synovium, normally functions to produce lubricating fluid for these areas. A ganglion is a cyst formed by the synovium that is filled with a thick jelly-like fluid.While ganglia can follow local trauma to the tendon or joint, they usually form for unknown reasons.anglia can form around any joint, but they are most frequently found in the wrist and ankles. They are usually painless and often barely visible as localized swellings. They typically do not appear to be inflamed. The largest ganglions form behind the back of the knee, causing a sense of fullness or tightness.