Joint Replacement Surgery Knee joint replacement is a procedure that involves replacing an injured or ailing knee with an artificial joint, or prosthesis. The prosthesis is made of metal alloys, plastics, and polymers. It mimics the function of a knee. According to the American Academy of Orthopaedic Surgeons (AAOS), replacement knees can fit your needs and specifications. When selecting a prosthetic knee, your doctor will take into account your