Sa Sa Sartorius! So many students end up singing sartorius to the rhythm of No No Notorious from Notorious B.I.G. There are several questions about this muscle that may pop up on your licensure exam. We’ll explore attachments, actions, and etymology.
Sartorius’ claim to fame is that it is the longest muscle of the body. Make a note of that, because you may see that question on a school or licensure exam. This muscle runs diagonally across the anterior femur. It is also the most superficial muscle of the anterior thigh. It’s a thin muscle, so despite it being superficial it is hard to differentiate.
The sartorius originates from the ASIS (anterior superior iliac spine) and inserts on the proximal, medial tibia through the pes anserinus tendon. The ASIS is the bony landmark on your hip that sticks the farthest anterior (forward). Pes anserinus means goose foot. It is a special tendon that three muscles, including sartorius, attach to. The way the tendon splits for the three muscles gives it the appearance of a goose foot… to somebody. Names are never creative, but sometimes what anatomists see can be. Sartorius’ actions can actually be explained by what sartorius means. It is derived from sartor, the Latin word for tailor.
Once upon a time tailors would sit cross legged on their tables while handling their garments. The actions of the sartorius are hip flexion, hip lateral rotation, hip abduction, knee flexion, and medial rotation of the flexed knee. I imagine you’re sitting as you read this. I want you to use your right leg. We’re going to try to get close to anatomical position. Start with a straight leg position with the heel touching the ground and your toes pointing up. Now I want you to flex your hip (raise your lower limb so your foot is up in the air). Then I want you to laterally rotate your hip (turn your lower limb so that your toes are pointing to the right). Now slightly abduct your hip (move your lower limb slightly away from center towards the right). Finally flex your knee (bend your knee until you have crossed your leg across the left thigh). You have successfully used your sartorius.
I didn’t forget about the final action. Most students think that you can’t rotate your knee. Usually you stick your leg in front of you and try to turn your foot out without using the femur. If you try from a straight knee position you’re correct, it’s impossible. But if you try while seated you’ll see it’s possible. I want you to sit with both feet on the ground. Now lift the heel of one foot up leaving the ball of the foot on the ground. Begin swinging your heel back and forth, like you’re trying to put out a cigarette with the ball of your foot. Magic, your knee rotated without breaking.
You can strip this muscle from attachment to insertion using your fingertips or palm. Sometimes I like to follow this muscle using sun and moon on the thigh. If this muscle is tight it could stop piriformis from getting a good stretch.
Recap: longest muscle of the body, most superficial muscle of the anterior thigh. Runs from ASIS to proximal, medial tibia. Innervated by the femoral nerve and its actions are hip flexion, hip lateral rotation, hip abduction, knee flexion, and medial rotation of the flexed knee.