Popliteus muscle assists in flexing the leg upon the thigh; when the leg is flexed, it will rotate the tibia inward. It is especially called into action at the beginning of the act of bending the knee, inasmuch as it produces the slight inward rotation of the tibia, which is essential in the early stage of this movement. When the knee is in full extension, the femur slightly medially rotates on the tibia to lock the knee joint in place. Popliteus is often referred to as the "Key" to unlocking the knee since it begins knee flexion by laterally rotating the femur
Vancleavea of archosaurs as well as the internal trochanter of basal archosauriforms. The midshaft of the femur is circular in cross-section. The lower portion of the femur includes both a medial condyle (which connects to the tibia) and a lateral condyle (which connects to the fibula), although neither of these knobs are particularly strongly developed. In general, the femur of Vancleavea is intermediate in structure between basal archosauriforms and archosaurs. The tibia and fibula (lower leg bones) are both slightly curved away from the center of the leg. They are also thinnest at their respective midshafts. The front edge of the