Sartorius
Thigh · Lower Limb
The sartorius is the longest muscle in the body, a narrow strap that runs diagonally across the front of the thigh. It arises from the anterior superior iliac spine and descends obliquely and medially to insert on the superomedial surface of the tibia as part of the pes anserinus. Crossing both the hip and the knee, it flexes, abducts, and laterally rotates the hip while also flexing the knee, the combination of movements used to sit in a cross-legged position. It is supplied by the femoral nerve (L2, L3).
Origin, Insertion, Action & Nerve
Origin
Anterior superior iliac spine (ASIS)
Insertion
Superomedial surface of tibia (pes anserinus)
Action
Flexion, abduction, and lateral rotation of hip; flexion of knee
Nerve
Femoral nerve (L2, L3)
Attachments explained
The Sartorius is defined first by where it attaches. Its origin is the more fixed anchor, usually the proximal or more stable end that stays put during contraction, while its insertion is the more mobile point that is pulled toward the origin when the muscle shortens.
Origin
Anterior superior iliac spine (ASIS)
Insertion
Superomedial surface of tibia (pes anserinus)
Action & function
When the Sartorius contracts, it produces the following movements: Flexion, abduction, and lateral rotation of hip; flexion of knee.
As part of the Thigh group of the Lower Limb, it works alongside neighbouring muscles to generate smooth, coordinated movement and to stabilise the structures it acts on.
Nerve supply & clinical relevance
The Sartorius receives its nerve supply from the Femoral nerve (L2, L3). This nerve carries fibres from spinal segment(s) L2, L3.
Because a muscle can only contract when its nerve is intact, injury to the Femoral nerve or to its spinal roots (L2, L3) can weaken or paralyse the Sartorius, impairing the movements it normally produces (flexion, abduction, and lateral rotation of hip). This is why knowing the innervation is central to localising nerve lesions in clinical practice.
How to study the Sartorius (the OIANS method)
Learn the sartorius through the cross-legged sitting posture, which is the origin of its name from the Latin for tailor. That single motion combines all of its actions at once: flexion, abduction, and lateral rotation at the hip together with flexion at the knee. Tracing its diagonal course from the anterior superior iliac spine across the thigh to the medial tibia makes each of those actions predictable.
Remember it as one of the three muscles forming the pes anserinus on the superomedial tibia, alongside gracilis and semitendinosus. Because it is supplied by the femoral nerve (L2, L3), it also serves as the lateral border of the femoral triangle, a landmark that ties its position to the neurovascular anatomy of the upper thigh.
Frequently asked questions
Where is the Sartorius located?
The Sartorius is a muscle of the Thigh group, located in the Lower Limb.
What is the origin of the Sartorius?
Anterior superior iliac spine (ASIS)
What is the insertion of the Sartorius?
Superomedial surface of tibia (pes anserinus)
What movements does the Sartorius produce?
Flexion, abduction, and lateral rotation of hip; flexion of knee
What nerve supplies the Sartorius?
Femoral nerve (L2, L3)
Is the Sartorius free to study in OIANS?
The Sartorius is always free to browse. Its full origin, insertion, action and nerve details are open to everyone in the Muscle Directory. Quiz and Flashcard practice for the Lower Limb is part of the one-time Lifetime upgrade, though; only the Upper Limb decks are free to test yourself on.
Related muscles
Study the Sartorius
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