Amputation is surgery done to remove a limb or part of a limb. It's done when tissue in the limb is diseased or damaged and cannot be healed. The surgeon saves as much of your limb as possible. This may include joints, such as the knee. But you may not know before the surgery how much of the limb will remain. Amputation is meant to restore function. Removing your diseased or damaged limb can improve your health. Common causes of amputation include peripheral artery disease that causes poor blood supply to an area due to injury,diabetes, infection, and cancer.