A sac filled with fluid forms at the back of the knee. While both adults and children can develop these cysts, the causes might differ based on age.
In children, the condition might stem from an inflamed bursa (a fluid-filled cushion) located behind the knee. The exact reason for this is unclear, but it’s not associated with any knee issues. Typically, these cysts don’t show any symptoms and often go away on their own.
In adults, these cysts often emerge from conditions leading to prolonged swelling or a buildup of fluid within the knee joint. Osteoarthritis is one potential cause. Other causes can be injuries to the meniscus (the cartilage inside the knee) or ligament damage, allowing the synovial fluid (which keeps joints lubricated) to leak from the joint capsule.
Many popliteal cysts resolve on their own, but some might burst, mimicking the symptoms of a deep vein thrombosis (DVT). Before opting for treatments like rest and pain-relieving medications, it’s essential to rule out a DVT diagnosis. In certain instances, surgical removal of the cyst may be necessary.