define subchondral cyst
Subchondral cyst formation is characteristic of osteoarthritis and can be routinely found on x-rays. A subchondral cyst is a fluid-filled sac that extrudes from the joint, consisting of thickened joint material (mostly hyaluronic acid, a substance found in the normal joint fluid that serves to lubricate the joint). Subchondral bone is the layer of bone just below the cartilage.