Behind the knee is the popliteal fossa, which contains the popliteal artery, the common peroneal nerve, and other important structures. Popliteal fossa pain and other symptoms occur when diseases such as popliteal cysts and popliteal tendonitis occur. The popliteal fossa, like the elbow fossa, is an area surrounded by ligaments behind the joint. The popliteal fossa is located behind the knee. It is surrounded by the tendons of the biceps femoris muscle and other muscles, and within it are structures such as the popliteal artery and its articular branches, the popliteal vein, the common peroneal nerve, and the tibial nerve. When inflammation and trauma occur within the popliteal fossa, pathological changes such as popliteal cysts and popliteal tendonitis can occur. In addition to causing localized pain, lumps and other symptoms, diseases such as popliteal cysts can cause the aforementioned neurovascular compression, resulting in abnormal manifestations such as numbness and pain in the lower leg.