The body's longest muscle
The sartorius is the longest muscle in your body. In a grown-up, it's about 20 inches long. That's almost as long as two school rulers!
It starts at a bony point at the front of your hip. Then it crosses the front of your thigh on a slant and ends on the inside of your knee, on your shin bone.
Try it: put your hands on your hips. Feel the pointy bone at the front? That's where your sartorius begins.
The tailor's muscle
Sartorius comes from sartor, the Latin word for tailor. A tailor is a person who sews clothes.
Long ago, tailors often sat cross-legged while they sewed. Sitting that way uses this muscle. It lifts your thigh, turns it out and bends your knee.
Try it: sit cross-legged on the floor, or put one ankle up on the other knee. Your sartorius helped you get there.
Long but thin
The sartorius is long, but it's thin, more like a ribbon than a rope. So it isn't one of the strongest muscles.
Instead, it's a helper. It works with bigger muscles when you lift your knee to march, climb or kick a ball with the inside of your foot.