WHAT IS A MUCOUS CYST?
A mucous cyst is a small fluid-filled sac that comes from the joint closest to your fingernail on the thumb or fingers. It can occasionally drain thin or thick fluid and can cause the nail to form a small ridge in it. The cyst comes from a joint that has arthritis which is the loss of the normal smooth cartilage over time. The cyst can be painful and even get infected.