The Sartorius muscle is a long, thin muscle located in the front of the thigh. It runs from the outer hip, specifically the iliac spine, down to the inner knee. This muscle is responsible for flexing the hip and knee, as well as allowing the leg to rotate outward. The Sartorius is often referred to as the longest muscle in the human body. It plays a crucial role in activities such as walking, running, and sitting cross-legged. Its name comes from the Latin word for "tailor," as it helps in the position that tailors traditionally used when sewing.