Which exercises strengthen the Popliteus muscle? What is the action of that muscle?
It will give us a chance to delve into the world of functional anatomy. Far too long we have been looking at anatomy from a cadaver’s perspective. What I mean by that is, most of the anatomy that is available in the academic world and the fitness world has been based on cadaver studies. What has been done is to locate the muscle in question, cut the insertion and pull on it. Whatever bone moves in whatever direction is what we have been calling the action of that muscle. The problem with that logic is that it just isn’t logical……… Here is why. The first reason that comes to mind is that the individual is not alive, therefore the neural system is not active. We have learned from even our most fundamental physiology courses and weekend certifications that the muscles contract from a stimulus from the neural system. The second blaring problem with cadaver or gross anatomy is that the limb being pulled on a cadaver is acting in an open chained system and when we function in gait and in an upright position the lower torso will likely function in a closed chain environment and will have to deal with GRF or ground reactive forces. There are many other reasons why doing gross anatomy will not give you an accurate account of what the muscle actually does, but those two should be enough for now.
Gross anatomy will tell us that the popliteus will help to concentrically flex the knee. If it works concentrically to accelerate knee flexion, it works eccentrically to decelerate knee extension, and works dynamically to stabilize the joint. It’s origin is the lateral condyle of the femur and the insertion is the posterior aspect of the proximal tibia. Basically, it is located behind your knee where it bends, slightly down toward the top of your calf. We must always remember that muscles work in groups, or synergies. It is a skewed view of the body when we try to isolate muscle function. The brain stimulates groups of muscles to produce and reduce force, when we try to isolate any given muscle we will throw off the natural balance between the synergies. Functionally, the popliteus stabilizes and eccentrically controls the tibio-femoral external rotation or force production during knee extension. The popliteus will concentrically work when we pronate or reduce force at heel strike. Flexion at the knee joint is a reduction of force. We flex the knee when the heel strikes and the forefoot absorbs the ground reaction forces. The weight of your body and gravity practically force your knee into flexion. We wouldn’t imagine it would need too much work in the concentric phase. If your client is having pain behind the knee and you think it may be in the popliteus, I would look to see if they are constantly standing with their knees locked. This will cause undo eccentric stress on the popliteus, which can lead to overload. Instead of looking to work the popliteus, a suggestion would be to look at the kinetic chain and see what musculature at the foot and ankle and/or what musculature at the hip is not working efficiently. The first set of muscles I would look at would be the hamstrings. The hamstrings share in the same functions of eccentrically decelerating knee extension, concentrically accelerating knee flexion and dynamically stabilizing the tibio-femoral joint. They are a much bigger muscle to identify insufficiencies and correct imbalances.