|Muscles of lower extremity. (Rectus femoris removed to reveal the vastus intermedius.)|
|Gray's||subject #128 470|
|Origin||inferior to the anterior superior iliac spine|
|Insertion||anteromedial surface of the upper tibia in the pes anserinus|
|Nerve||femoral nerve (sometimes from the intermediate cutaneous nerve of thigh)|
|Actions||Flexion, abduction, and lateral rotation of the hip, flexion of the knee|
The sartorius muscle – the longest muscle in the human body – is a long thin muscle that runs down the length of the thigh in the anterior compartment. Its upper portion forms the lateral border of the femoral triangle.
Origin and insertion 
This tendon curves anteriorly to join the tendons of the gracilis and semitendinosus muscles which together form the pes anserinus, finally inserting into the proximal part of the tibia on the medial surface of its body.
There are four hypotheses as to the genesis of the name: One is that this name was chosen in reference to the cross-legged position in which tailors once sat. Another is that it refers to the location of the inferior portion of the muscle being the "inseam" or area of the inner thigh tailors commonly measure when fitting a pant. A third is that the muscle closely resembles a tailor's ribbon. Additionally, antique sewing machines required continuous cross body pedalling. This combination of lateral rotation and flexion of the hip and flexion of the knee gave tailors particularly enlarged sartorius muscles.
Assists in flexing, adduction/abduction (weak) and lateral rotation of hip, and flexion of knee. Looking at the bottom of one's foot, as if checking to see if one had stepped in gum, demonstrates all four actions of sartorius.
Situated in the anterior fascial compartment of the thigh, the sartorius is innervated via the anterior (or superficial) branch of the femoral nerve (AORN Journal, J. Murauski). The femoral nerve is responsible for both sensory and motor components in the sartorius and provides proprioceptive feedback for the muscle (Anatomy and Physiology 5th edition, K. Saladin)
One of the many conditions that can disrupt the use of the sartorius is pes anserine bursitis, an inflammatory condition of the medial portion of the knee. This condition usually occurs in athletes from overuse and is characterized by pain, swelling and tenderness. The pes anserinus is made up from the tendons of the gracilis, semitendinosus, and sartorius muscles; these tendons attach on to the anteromedial proximal tibia. When inflammation of the bursa underlying the tendons occurs they separate from the head of the tibia (eMedicine, MD. M. Glencross).
The muscle may be absent (Scott-Conner, Carol E. H.; David L. Dawson (2003). http://books.google.com/books?id=06GvkEYPg20C
|chapterurl= missing title (help). Operative Anatomy. Lippincott Williams & Wilkins. ISBN 0-7817-3529-7. p.606).
Additional images 
- 208339022 at GPnotebook
- LUC sart
- SUNY Labs 14:st-0407
- Cross section at UV pembody/body15a
- Cross section at UV pelvis/pelvis-e12-15