The primary indications for joint replacement surgery include severe lower extremity pain that prevents individuals from performing normal daily activities. The level of pain experienced by these patients cannot be managed successfully with oral medications, physical therapy, or joint injections of steroids or hyaluronic acid. The source of the pain most commonly is a result of arthritic changes in the joint; the arthritis may be due to osteoarthritis, rheumatoid arthritis, or traumatic arthritis. Patients who are appropriate candidates for partial joint replacement surgery also may experience joint stiffness that interferes with their normal daily activities. In addition, there usually is radiographic evidence of changes in the joint caused by the arthritic process. Joint damage is evaluated radiographically in order to classify the severity of the joint disease. Partial joint replacement surgery is performed to replace the diseased parts of the joint with prosthesis. There are a variety of options that surgeons and patients can choose for their joint replacement surgery. There are many different joint replacement component systems manufactured by several different companies; some systems are recommended for particular types of patients while others can be used in a greater number of patients. Recently, new techniques have been introduced that are classified as minimally invasive because they require smaller surgical incisions to implant standard joint prostheses. Patients who are younger, thinner, and in better overall health are usually the best surgical candidates for minimally invasive procedures.