Episode 154: "Reducing knee pain with Popliteus release" The popliteus is a muscle that runs from the lateral epicondyle of the femur to the posterior surface of the tibia. Because of its orientation, it internally rotates the tibia and externally rotates the femur. This action allows the knee to become “unlocked,” taking the knee from an extended (straight) position to a flexed (bent) one. The significance an injury to the popliteus is particularly relevant to serious runners and triathletes. W