The need for total knee arthroplasty (TKA), replacement, is growing for both older and younger patients - and with this growth, physicians need to understand the reasons behind the epidemiology (age and distribution of who is receiving the replacements), the use of partial versus total replacements, and surgical procedures. The author of this article reviews the latest research regarding how the procedure is changing and what may be coming in the future.

In the United States, the use of knee arthroplasty has grown considerably since 1971. Researchers found there was an over 400 percent increase of TKA between those done in the period between 1971 to 1975 and 2000 to 2003 - with the largest increase being in the younger patients, those under 55 years old. This compares with the rise of total hip replacements of only 55 percent. More women required TKA than did men except for older patients over the age of 80 years. The researchers also found that the reasons for TKAs changed: during the period in the 70s, 51 percent of TKAs were done for osteoarthritis, in the 2000s, this rose to 92 percent. Forecasts estimate that the number of first time TKAs (primary TKAs) will increase from 450,400 to 3.48 million by the year 2030, while there will only be an increase from 208,600 hip replacements to 572,100.

When looking at the actual treatments, the researchers found that unicompartmental knee arthritis (arthritis in one section of the knee) requiring only partial knee replacement, were frequently in younger patients. One study reviewed by the author of this article found that there was a better outcome for patients who underwent a procedure that involved metal-backed components over all-polyethylene tibial (shin bone) components. They found more complications associated with the second type, as well. When looking at how the surgery was performed, traditionally or minimally invasive, the patients who had the minimally invasive approach were found to have a better range of motion up to 3 years following the surgery. Another study of the same techniques (traditional vs. minimally invasive) found there were more complications with the minimally invasive approach. These patients experienced problems that required revisions to the knees at a higher rate than those who had the traditional surgery.

Another procedure, the patellofemoral arthroplasty (where the femur and the kneecap join), is being performed more often. This procedure appears to be successful and patients are doing well.

Computers are making their presence felt in the operating room as part of the TKA process. Using computers, surgeons have tried to improve on their ability to line up the limbs more accurately. However, surgery time was increased with the computer (by 27 minutes), as well as the need for blood transfusions.

Techniques during surgery also play a role in patient outcome. In one study, patients received, during surgery, a combination of 3 medications: ropivacaine, ketorolac, and epinephrine, directly into the knee. One day after surgery, they received ropivacaine into the knee again. These patients, who received morphine for pain relief as needed, were compared with patients who had morphine only. The patients in the first group had no complications due to the medication. They also needed less morphine than the control group, although there were no significant differences between the two groups regarding when they were discharged from hospital and how well they functioned.

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