Total knee replacement is a surgical procedure in which injured or damaged parts of the knee joint are replaced with artificial parts. The procedure is performed by separating the muscles and ligaments around the knee to expose the knee capsule (the tough, gristlelike tissue surrounding the knee joint). The capsule is opened, exposing the inside of the joint. The ends of the thigh bone (femur) and the shin bone (tibia) are removed and often the underside of the kneecap (patella) is removed. The artificial parts are cemented into place. Your new knee will consist of a metal shell on the end of the femur, a metal and plastic trough on the tibia, and if needed, a plastic button in the kneecap.

Risks of total knee replacement
Total knee replacement is a major operation. About one patient in four develops one or more complications. The effect of most complications is that you must stay in the hospital longer.
The most common complications are not directly related to the knee and usually do not affect the result of the operations. These complications include urinary tract infection, blood clots in a leg, or blood clots in a lung.
Complications affecting the knee are less common, but in these cases the operation may not be as successful.

These complications include:

A few complications such as infection, loosening of prosthesis, and stiffness may require reoperation. Infected artificial knees sometimes have to be removed. This would leave a stiff leg about one to three inches shorter than normal. However, your leg would usually be reasonably comfortable, and you would be able to walk with the aid of a cane or crutches, and a shoe lift. After a course of antibiotics the surgery can often be repeated.

Patients should consider a total knee replacement
Total knee replacement surgery is considered for patients whose knee joints have been damaged by either progressive arthritis, trauma, or other rare destructive diseases of the joint. The most common reason for knee replacement in the United States is severe osteoarthritis of the knees.
For further information, please see the Osteoarthritis article of MedicineNet.com. Regardless of the cause of the damage to the joint, the resulting progressively increasing pain and stiffness, and decreasing daily function lead the patient to consider total knee replacement. Decisions regarding whether or when to undergo knee replacement surgery are not easy. Patients should understand the risks as well as the benefits before making these decisions.