The Sartorius is the ribbon-like muscle that passes obliquely (lateral to medial) across the length of the thigh. It is the longest muscle in the body, and acts across two joints. It flexes the thigh and participates in flexion of the lower leg. It abducts and laterally rotates the thigh. None of the actions of the sartorius are strong. The femoral nerve innervates the sartorius muscle.