The thigh arteries, courtesy Wikimedia Commons
The femoral artery runs through the groin and supplies blood to the legs. It's one of the largest arteries in the body because of the need to supply blood to the muscles of the legs, and often has the highest blood pressure because it's the largest artery below the heart, and therefore blood pressure need not fight against the force of gravity. In addition, the artery lies quite close to the surface of the skin and is very vulnerable. As a result, a puncture of the femoral artery is a life threatening injury as a patient can bleed to death in a matter of minutes.
The result of a severed femoral artery is clearly and graphically depicted at the beginning of the episode Frozen.