The Nature of the Devices: Both the natural aging process and a specific injury can degrade knee and hip joints. As a result, Zimmer, Inc., Stryker, Corporation, DuPuy Orthopaedicts, Inc., and other companies manufacture hip and knee replacements; they are made wholly of metal, of metal and ceramic, or of metal and plastic.
All knee replacements have tibula, fibula, and patella (knee cap) components that perform the same functions as a real knee joint. Knee-replacement parts may be cemented to adjoining leg bones or work without cement.