knee replacement surgery you will be prepared or "prepped." First, the IV line will be inserted through a vein in your arm or hand, allowing fluid to be injected into a vein and medication to flow directly into your bloodstream. In addition, the skin around the incision site will be trimmed. you want to avoid any situation that can invite any kind of germs into the surgical area. In most cases, spinal anesthesia is given to the patients. This is the best anesthetic because it makes you completely numb from the waist down and the risk is very small. In some patients, this kind of general anesthesia treatment follow, in which you are completely asleep, may be needed.