Situated at the knee joint, the popliteus is a small muscle that arises from both the femur’s lateral condyle, and the lateral meniscus’ posterior horn and then runs along toward the tibia where it finally connects into the soleus muscle. The popliteus muscle is notable for being the only posterior muscle in the lower leg that acts only on the knee versus the gastrocnemius for example, which acts on both the knee joint and the ankle joint.
For such a small muscle, the popliteus is quite important. Without it, neither standing nor bending would be possible as we’d fall right over. Popliteus facilitates bending of the knee, by generating a slight rotation inward of the tibia. On the other hand, Popliteus locks the joint in place by slightly rotating the femur on the tibia. Often, people refer to popliteus as key owing to its strange twisting action on the femur. Control for this muscle comes from the tibial nerve from spinal roots L5 and S1.