Anatomy and supply
The sartorius muscle is a long, slim, superficially running extensor of the thigh musculature. It originates from the anterior superior iliac spine of the pelvic bone and runs spirally towards the knee region. There it inserts at the pes anserinus medially from the tibial tuberosity. In its entire course the muscle is covered by a fascial duplication of the fascia lata. The innervation is supplied by the femoral nerve (L2-4).
Topographically the sartorius muscle forms the lateral border of the femoral triangle (Scarpa’s triangle) where the large vessels of the thigh pass through. For this reason the muscle serves as a leading structure when surgically accessing the femoral artery.
The sartorius muscle is a two-joint muscle and moves both the hip and knee joint. Even though anatomically it ranks among the extensors of the thigh its contraction truly causes a flexion of the hip joint. This is because it is located in the ventral (extensor) compartment of the thigh. In addition, it is involved in the abduction and outward rotation of the hip joint.
In the knee joint, it forces a flexion and inward rotation. The flexion movement is the result of the tendon inserting at the knee joint behind the flexion-extension axis. When all five movements are executed simultaneously the legs would cross like in a tailor seat. Therefore, the “tailor’s muscle” is most easily palpable in this position.
The pes anserine bursa located at the insertion of the sartorius muscle can inflame (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 muscle). If the inflammation is overseen or poorly treated (rest, cooling, pain medication, local corticoid injection if necessary) the bursitis often becomes chronic.