Hi everyone! This Joao from Kenhub, and on this tutorial, we will talk about the different functions of the sartorius muscle – this muscle that you now see isolated on the screen. Before we talk about the actual movements that this muscle is able to do on different joints of the lower limb, let me introduce you to the sartorius. As you can see on the image, it is a very long, slim muscle that extends from your pelvis all the way to your knee. The sartorius is a superficial muscle which means that you can't find any muscle lying on top of it.
The innervation of the sartorius muscle is carried out by the femoral nerve, which is the structure seen here highlighted in green on the image. Every muscle in your body is attached to something – usually bones – and the sartorius muscle is no exception. It originates from the anterior superior iliac spine of the pelvic bone and then runs spirally all the way down to the knee where it attaches. To be more precise, the muscle will insert at a structure called pes anserinus, which is a collection of muscle tendons that attach to the anteromedial surface of the proximal end of the tibia. From that information, you get a clue to what joints are going to move when the sartorius muscle is contracting. They are the hip joint formed by the head of the femur and the acetabulum, and the knee joint which is the meeting point for the distal end of the femur, the proximal end of the tibia and the patella, which is this bone that you can feel in front of your knee.
Now let's talk about the different functions of the sartorius muscle. We will start with the movements that the muscle is involved in at the hip joint. First movement at the hip point that we're going to be talking about is flexion. You can see now how the sartorius muscle is flexing the thigh at the hip joint by bringing the thigh towards the front of the body. Even though anatomically this muscle is considered to be an extensor of the thigh, its contraction is responsible for flexion here. Another movement that happens at the hip joint is abduction which is, as you see on the screen, the sartorius involved in bringing the lower limb away from the midline of the body. The third type of movement the sartorius is involved in at the hip is external rotation of this joint, which is essentially when you rotate your leg to the side or laterally.
We're going to continue on and it is time for us to talk about the movements that the sartorius muscle is able to produce at the knee joint. The first movement we're going to talk about is flexion of the knee. When contracted, the sartorius can contribute to flexion of this joint as you see now on the screen. This movement happens when you bring your leg towards the back of your body. The second and last type of movement caused by the sartorius is called internal rotation. In order to show you this movement, we have to flex the knee at a 90-degree angle. So what you see now on the screen is what it would look like if you were sitting on a chair. Then when the knee is flexed, internal rotation is possible which is when you rotate the lower leg towards the midline of your body. Now, why is internal rotation stronger when the knee is flexed? Well that is due to the fact that the angle between the head of the tibia and the insertion tendon is almost a perfect 90-degree angle allowing the muscle to then pull the tibia inwards with maximum strength.
And this is it for the functions of the sartorius muscle. I hope you enjoyed it and I'll see you next time.
Now that you just completed this video tutorial, then it’s time for you to continue your learning experience by testing and also applying your knowledge. There are three ways you can do so here at Kenhub. The first one is by clicking on our “start training” button, the second one is by browsing through our related articles library, and the third one is by checking out our atlas.
Now, good luck everyone, and I will see you next time.