The sartorius, the “tailor’s muscle” (Latin sartus, patched or repaired), is long and ribbon-like. It passes lateral to medial across the superoanterior part of the thigh. The sartorius lies superficially in the anterior compartment, within its own relatively distinct fascial sheath. It descends inferiorly as far as the medial side of the knee.

The sartorius, the longest muscle in the body, acts across two joints. It flexes the hip joint and participates in flexion of the knee joint. It also weakly abducts the thigh and laterally rotates it. The actions of both sartorius muscles bring the lower limbs into the cross-legged sitting position. None of the actions of the sartorius is strong; therefore, it is mainly a synergist, acting with other thigh muscles that produce these movements.