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Sartorius muscle: want to learn more about it?

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Sartorius muscle

The sartorius muscle is the longest muscle in the human body. Together with the quadriceps femoris, it belongs to the anterior (extensor) muscles of the thigh.

The sartorius muscle has an oblique course throughout the thigh; it arises from the anterior superior iliac spine, crosses to the medial side of the thigh, and finally inserts to the medial side of the proximal tibia.

Due to its oblique course, the sartorius muscle doesn’t extend the thigh, as one would expect from a muscle of the anterior compartment. Instead, the sartorius muscle flexes, abducts and externally rotates the thigh, and flexes and internally rotates the leg.

Key facts about sartorius muscle
Origin Anterior superior iliac spine (ASIS)
Insertion Proximal end of tibia below medial condyle (via pes anserinus)
Innervation Femoral nerve (L2-L4)
Blood supply Proximal third: branches of femoral artery, deep femoral artery, artery of quadriceps, lateral circumflex femoral artery
Middle third: branches of femoral artery
Distal third: branches of femoral and descending genicular arteries
Function

Hip joint: thigh flexion, thigh abduction, thigh external rotation

Knee joint: leg flexion, leg internal rotation

This article will discuss the anatomy and function of the sartorius muscle.

Origin and insertion

The sartorius muscle originates by a round tendon from the anterior superior iliac spine and the upper half of the notch between the anterior superior iliac spine and the anterior inferior iliac spine. The fibers form a thin, flat muscle, which extends inferomedially across the anterior surface of the thigh.

The muscle descends in an almost vertical fashion through the medial aspect of the thigh. It crosses the medial side of the knee joint and then inserts onto the medial aspect of the proximal tibia, anterior to the gracilis and semitendinosus muscles.

The inserting tendons of these three muscles form a wide aponeurotic sheath called the pes anserinus. Some fibers from the inferior part of the tendon blend with the medial collateral ligament of the knee joint, and the deep fascia over the medial aspect of the leg, while some superior fibers blend with the knee joint capsule. These connections contribute to the medial stability of the knee joint.

Relations

The sartorius muscle lies superficially in the thigh, with only fascia and skin over its surface. Deep to the sartorius is the quadriceps femoris muscle.

As it crosses from the lateral to the medial side of the thigh, the sartorius muscle crosses the surfaces of the iliopsoas, pectineus and adductor longus muscles. The tensor fasciae latae muscle originates just lateral to the proximal attachment of the sartorius muscle.

The medial edge of the sartorius forms the lateral border of an important anatomical space known as the femoral triangle. The triangle is completed superiorly by the inguinal ligament and medially by the medial margin of the adductor longus muscle. The structures found within the triangle, the femoral artery, vein and nerve, therefore, lie medial to the sartorius. The femoral artery continues inferiorly, deep to the sartorius.

In order to easily remember the borders of the femoral triangle, you can use the mnemonic SAIL which stands for:

  • Sartorius
  • Adductor longus
  • Inguinal Ligament

Innervation

Sartorius receives its innervation from the femoral nerve L2 and L3.

Blood supply

As sartorius is such a long muscle, it comes as no surprise that it requires extensive vascular supply from several sources:

  • The proximal third may receive its vascular supply from the branches of the femoral, deep femoral, lateral circumflex femoral arteries and/or artery of quadriceps (branch of either the deep femoral or lateral circumflex femoral artery).
  • The middle third is supplied by branches of the femoral artery.
  • The distal third receives blood supply from the femoral artery and descending genicular artery.

Function

The sartorius muscle crosses both the hip and knee joints, producing movements on both of them. At the hip joint it is capable of flexion, external rotation and abduction of the leg. The contraction of sartorius can also cause flexion of the knee joint and inward, or medial, rotation of the tibia against the femur.

The combination of all these movements allows an individual to sit in a cross-legged position. However, movements created by the contraction of sartorius are not limited to that single function. It is also suggested that sartorius may play an important role in climbing.

Clinical relations

The pes anserine bursa located at the insertion of the sartorius muscle can become inflammed (pes anserine bursitis) when chronically overstrained (e.g. when jogging or breaststroking).

Common symptoms are pain, swelling and a functional impairment of the three muscles inserting at the pes anserinus (sartorius, semitendinosus and gracilis muscles). If the inflammation is overseen or poorly treated (rest, cooling, pain medication, local corticoid injection if necessary) the bursitis often becomes chronic.

Sartorius muscle: want to learn more about it?

Our engaging videos, interactive quizzes, in-depth articles and HD atlas are here to get you top results faster.

What do you prefer to learn with?

“I would honestly say that Kenhub cut my study time in half.” – Read more. Kim Bengochea Kim Bengochea, Regis University, Denver

Show references

References:

  • Moore, K. L., Dalley, A. F., & Agur, A. M. R. (2014). Clinically Oriented Anatomy (7th ed.). Philadelphia, PA: Lippincott Williams & Wilkins.
  • Soames, R., Palastanga, N. and Richardson, P., 2012. Anatomy And Human Movement. 6th ed. Elsevier Ltd.
  • Standring, S. (2016). Gray's Anatomy (41tst ed.). Edinburgh: Elsevier Churchill Livingstone.

Illustrators:

  • Sartorius Muscle (Musculus sartorius) - Liene Znotina 
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