Decoding Knee Pain: 10 Typical Causes

8. Popliteal Cyst

A popliteal cyst or bakers cyst is a fluid-filled bulge at the back of the knee. It occurs when excess fluid is pushed into the tissue behind the knee, and generally develops due to knee arthritis or gout. Common symptoms associated with popliteal cysts include tightness behind the knee, slight pain in the upper calf, swelling, and stiffness behind the knee. The knee may also make a popping or clicking sound or lock up. Often the pocket of fluid tears open and drains down the leg, which causes the swelling to spread. Generally, popliteal cysts go away on their own, or a doctor can drain the fluid.