A tourniquet is a device used to control the flow of blood temporarily. If you cut your knee really badly, the doctor might put a tourniquet on your thigh before operating — to control the blood flow to your knee.
A tourniquet is usually used for two purposes in medicine. In surgery, a tourniquet is used to stop the flow of blood to a limb while it is being operated on. In an emergency, a tourniquet is used to control blood loss. By compressing around the veins that bring blood to a limb, a tourniquet stops or slows the flow of blood temporarily.
