Causes. A popliteal cyst is caused by swelling in the knee which happens when the volume of fluid lubricating the knee joint increases. This causes an increase in pressure which forces some of the fluid into the space behind the knee. Baker’s cysts are strongly associated with all types of arthritis, including gout, but they can also be caused by an injury to the knee, particularly sports-related injuries. Baker’s cysts are more likely to affect women than men because women are at a higher risk of rheumatoid arthritis (RA) and osteoarthritis. They are also more common after the age of 40. Still, anyone can get a baker’s cyst.