DENVER -- Every year in the United States, thousands of knee replacement surgeries are performed on patients seeking relief from inflammation and severe pain.

These patients typically suffer from osteoarthritis (which causes cartilage in the knee to deteriorate), rheumatoid arthritis or a knee joint injury. Knee replacement surgery is performed to replace a damaged joint with a prosthetic one, allowing for greater mobility and less pain.

In arthroplasty, or total knee replacement (TKR) surgery, a metal or plastic prosthesis is put in place of severely damaged cartilage tissue to act as a new knee joint. Most knee replacement joints are designed to mimic the knee's natural gliding and bending motion. The surgery provides relief from chronic and debilitating pain in about 90 percent of patients for up to 15 years. According to the Mayo Clinic, in recent years TKR surgery has made many advances.

Early artificial knees were rudimentary hinges, but today's can be tailored to a patient's age, weight, activity level and overall health. Following surgery, patients typically remain in the hospital for two to four days. For about three to six weeks, patients require crutches and walkers to get around.

Risks of the surgery include infection, stiffness of the knee, blood clots in the leg vein or lungs, heart attack, stroke and nerve damage; however, the Mayo Clinic says fewer than two percent of patients who receive knee replacement surgery experience serious complications. The new knee joints are also at risk of breaking because of daily wear and tear. Those with the greatest risk of their new joint failing are young, obese males or those who have conditions that affect the joint.

Some surgeons are now using a new computer-guided imaging system during TKR surgery. The image-guided surgery (IGS), also known as computer-assisted surgery (CAS), assists surgeons in more accurately placing an artificial joint in the bone. The system works similarly to a satellite system in a car.

As the surgeon moves an instrument within the joint, the IGS camera calculates its exact position. The data is transmitted to a computer in the operating room and a model is created.

"The navigation gives us a tool of seeing the anatomy without actually looking at it," Robert Moukarzel, M.D., an orthopaedic surgeon at Ochsner Medical Center in Baton Rouge, La., said.

According to him, the procedure can be especially useful for those patients that are bull-legged or knock-need because their alignment is off. In these individuals, a straight line could not be drawn from the center of the hip, through the center of the knee and to the ankle, as you could in a patient with normal anatomy.

Dr. Moukarzel said no long term studies have been performed with this system to prove it works better with misaligned individuals, but better alignment would mean a longer lasting prosthesis. Another potential benefit of using this new technology is a shorter hospital stay.

Moukarzel said a recent study showed this surgery can cut the hospital stay by one day. Less bleeding and fewer pulmonary and cardiac complications have been observed using this new method. Patients were also walking sooner.