An artificial knee replaces a person's knee when the real knee is too painful, or the range of motion is compromised due to arthritis or other condition. In 2013, an artificial knee is made from titanium, and weighs about 10 ounces. When the physician does the surgery to replace a knee, he has to remove bone and tissue to add the knee. The weight of the bone and tissue that he removes is almost the same weight as the artificial knee, so it is almost an even swap. The artificial knee should last from 15 to 20 years.