The longest muscle in the human body is the sartorius muscle. It is a long, thin, strap-like muscle found in the anterior compartment of the thigh. The sartorius runs obliquely from the anterior superior iliac spine of the hip bone, crossing the thigh diagonally to insert on the medial side of the proximal tibia near the knee. This muscle spans both the hip and knee joints and functions in flexing, abducting, and externally rotating the thigh at the hip, and flexing the leg at the knee.
