Video: Popliteus muscle (3D)

Hi everyone! This is Joao from Kenhub, and in this tutorial, we will look at the functions of the popliteus muscle. You can see this muscle now isolated on the screen. Before we describe the actions, let’s first look at the popliteus in more detail.

This thin triangular-shaped muscle is located at the posterior aspect of the knee joint. Specifically, it is located deep within the popliteal fossa and helps form the floor of this space. We should recall that the popliteal fossa is the shallow diamond-shaped depression located at the posterior aspect of the knee.

Now looking at the popliteus muscle requires retraction of the muscles that form the boundaries of the popliteal fossa. This include then the biceps femoris, semitendinosus, and the medial and lateral heads of the gastrocnemius. We will also remove the plantaris muscle to allow full visualization of the popliteus muscle.

Located within the popliteal fossa is the tibial nerve which is responsible for innervating the popliteus. You can see the nerve highlighted in green in this image.

Now let’s look at the attachment points for the popliteus. It originates from the lateral condyle of the femur and the posterior horn of the lateral meniscus. It then travels inferomedial to insert on the tibia just superior to the soleal line. Muscles are only able to act on joints that they cross, therefore, the popliteus will only act on the knee joint.

When the knee fully extends, the femur medially rotates on the tibial plateau about five degrees which results in locking of the knee. You can feel this on yourself by standing up and fully extending your knee joints. In this position, your knees are locked, meaning that flexion cannot occur since the femoral condyles and the tibial plateau are not fully aligned. The popliteus works much like a key that unlocks the knee joint. It does so by reversing the locking mechanism through slight medial rotation of the tibia at the knee joint. With the femoral condyles and the tibial plateau now aligned, flexion can occur.

The popliteus’ ability to actually flex the knee, however, is negligible. The popliteus also functions to pull the lateral meniscus posteriorly as the knee flexes. This prevents the meniscus from becoming impinged. The actions of the popliteus muscle have now been fully described now, let’s take a look at what we’ve learned.

The popliteus works to unlock a fully extended knee joint by medially rotating the tibia about five degrees. This aligns then the tibial plateau with the femoral condyles permitting then flexion. Then we saw that the popliteus also functions to pull the lateral meniscus posteriorly during knee flexion. But remember this that the popliteus has a negligible effect on the actual flexion of the knee.

And this concludes this really short tutorial on the functions of the popliteus muscle. I hope you liked it and I will see you on the next one.