People can lose all or part of an arm or leg for a number of reasons. Common ones include
Circulation problems from atherosclerosis or diabetes. They may cause you to need an amputation.
Traumatic injuries, including from traffic accidents and military combat
Cancer
Birth defects
If you are missing an arm or leg, an artificial limb can sometimes replace it. The device, which is called a prosthesis, can help you to perform daily activities such as walking, eating, or dressing. Some artificial limbs let you function nearly as well as before.