Case study - lumbar synovial cyst Synovial cysts are abnormal fluid-filled sacs in joints in the spine. These cysts are benign, which means they are not cancerous. Synovial cysts typically develop as a result of degenerative changes that occur with aging. They can be found throughout the spine, but are most common in the lumbar region (low back). The spine has many joints. Synovial cysts develop in the facet joints of the spine. These are the joints between the bony projections at the back of th