Your Knee and How it Works
When a knee becomes diseased or injured, simple movements can be painful and take the joy out of life. Most people want relief from the pain and disability caused by severe arthritis. Your reasons for having surgery are very personal. Only you can finish this sentence: "If I didn't have pain, I would..." You and your doctor have decided that total knee replacement surgery may help relieve much of your pain.
The main benefit you may expect from total knee replacement is pain relief, which can be quite dramatic. Most patients will notice some soreness for several weeks or months after surgery. In most cases, however, pain-free motion of the knee joint will follow.
The Normal Knee
A joint is a structure in the body where the neds of two or more bones meet. The thighbone (femur) and the shinbone (tibia) meet to form the knee joint. The kneecap (patella) is in the front of the knee joint. The joint lining (synovium) makes fluid that lubricates the joint. Cartilage covers the ends of the knee bones. This cartilage "cushions" the knee for smooth, easy movement. The knee, a major weight-bearing joint, is held together by muscles and ligaments that allow your leg to bend and straighten so you can walk and climb stairs.
The Problem Knee
When a knee is diseased, such as with arthritis, the cartilage wears away. The bones become exposed and the rough surfaces grind together, causing pain.
There are many different types of arthritis. One major type is osteoarthritis, which is also called degenerative joint disease. Another form, rheumatoid arthritis, is a systemic disease that affects many parts of the body. There can also be joint destruction due to loss of blood supply (osteonecrosis) or from injuries (traumatic arthritis). After your condition has been accurately diagnosed, and if other medical treatments have failed to help you, the orthopedic surgeon can replace your diseased joint and soon relieve your pain. Total knee replacement is not done for minor arthritis pain.
Your New Knee
Total knee replacement surgery involves removing the diseased portion of the knee joint. 
An artificial knee, known as prosthesis, replaces it. There are generally three parts (components) to an artificial knee. The femoral prosthesis is placed on the end of the thighbone. The tibial prosthesis is placed on top of and covers the shinbone. The patellar prosthesis covers the underside of the kneecap. These implants are usually cemented in place and are most commonly made of metal and plastic. Special instruments are used to shape the bones for an exact fit, which is important for smooth, pain-free movements as the knee bends and straightens.
Your orthopedic surgeon will decide whether you will need just one or all three of these parts. The surgery usually takes approximately 1 � hours for one knee joint or 2 ½ hours for two knee joints, depending on the condition of your knee.