“What is the difference between a ganglion cyst and a synovial cyst?”

The difference is that a Synovial Cyst has a synovium (a thin film layer around the cyst) and a ganglion cyst does not have a synovium. As far as treatment goes, they are treated the same way, so the difference is not clinically important.

Good question - "Ganglion cyst" refers to a fluid filled cyst on the wrist. The cyst arises most commonly on the back of the lower wrist. It emerges from thin linings of wrist tendons most commonly. The cyst emerges up and out, is filled with thin fluid, and does not indicate disease. It rarely causes pain or discomfort, but it can become firm and can begin to be sore. It can be submerged with firm point pressure but this is not advisable. It can soften and disappear over weeks to months. It can appear because of some wrist strain or overuse but most often an exact cause is not clear. It can be surgically managed or even drained by a skilled operator. It hardly ever becomes inflamed or infected. It is best left alone - not to be pinched or squeezed repeatedly. These moves make more fluid seep into the sac. "Ganglion cyst" could be viewed as a "synovial cyst" but this is not precisely accurate. "Synovial cyst" refers to a pouch or diverticulum sac that emerges from the synovial membrane lining of a joint. "Synovial cyst" is most common in the back of the knee, where it is called "Baker's Cyst." Or "Synovial cyst" is also commonly diagnosed in the lumbar spine region, where strain and sprain ailments result in inflammatory fluid secretion, but the excess fluid does not have any "space" so it promotes an "extrusion" sac emerging from the lumbar vertebral line. The fluid in a synovial cyst is thicker, more inflamed, and longer lasting compared with a ganglion cyst
at the back of a wrist. It will not disappear or shrink and will warrant surgical remediation. It can be a source of discomfort in one's lower back because of the tight space there and the accompanying inflammation and inflammatory fluid. Similarly, a synovial cyst in the back of the knee, called Baker's Cyst, is also inflammatory and strain-related and it has discomfort and its natural history is to persist and grow. It is best managed with surgery.

Best,

Rex Mahnensmith, MD