Before anyone thinks legs are not vital organs, let me remind you of General Albert Sidney Johnston. He was wounded in the thigh at Shiloh, no one around him knew how to apply a tourniquet. Before they could get a doctor to him, a matter of less than 20, he bled to death.
That would be the femoral artery -- one of the largest arteries in the body. The main part of it extends from the inside of the hip near the groin to where it branches off at the knee.

I take it that "less than 20" means "less than 20 minutes".

Definitely worth protecting.