Knees wear out for a variety of reasons. These include inflammation from arthritis, injury or simple wear and tear. Total knee replacement (arthroplasty) is a surgery that is performed for severe degeneration of the knee joint.. A surgeon replaces lost cartilage with metal and plastic. More than 300,000 people undergo the procedure each year. This is typically done through an incision down the center of the knee. The incision averages 8 inches to 10 inches long Total knee replacement can be performed in the traditional method (8 inch to 10 inch incision). Or it can be performed using newer techniques (4 inch to 6 inch incision). The goal of knee replacement is to provide a pain-free knee that allows relatively normal activities and lasts for as long as possible. In order to achieve these goals, it is extremely important that the knee replacement be inserted in the best possible position. The bone and ligaments are prepared very carefully to allow the knee to be functional and durable. Using the current techniques, 90 percent to 95 percent of knee replacements should last 15 years or longer, Minimally invasive total knee arthroplasty is one method of performing a knee replacement. It uses a smaller incision. Minimally invasive total knee arthroplasty is a different way of performing the surgery. It uses an incision that is only 4 inches to 6 inches long. This means that potentially there will be less damage to the tissue around the knee.

The minimally invasive knee replacement technique attempts to accomplish all of this through a smaller incision. With the smaller incision come the potential benefits of a shorter hospital stay, a shorter recovery and a better looking scar. There is no reason to believe that the knee will function any better. Although there is no question that a knee can be put in through a smaller incision, it is still unknown whether it can be done as well. New ways to open the knee may be more important than the length of the incision. These are sometimes called "quad-sparing" because they protect the quadriceps (the muscle on the front of the thigh) and make the recovery easier.

Several early studies of MIS knee surgery have shown some benefits such as less blood loss, shorter hospital stays and better motion, while others have shown a higher rate of complications, suboptimal positioning of the knee implants and no real difference in the recovery. Unfortunately, we won't know if these new techniques affect the long-term function and durability of the knee replacement for 10 to 15 years. Long-term durability is much more important than whether you were in the hospital for 2 days or 4 days after surgery.

Research on the Horizon

Advocates of minimally invasive knee replacement are working to address concerns about accurate positioning of the knee replacement. They are combining the small incision with computer-guided instruments.