Replacing a knee joint with an artificial one—a procedure called knee arthroplasty—is a common treatment for severe arthritis: More than 350,000 knee replacement procedures are performed in the United States each year. Originally, the procedure was considered most appropriate for people age 60 to 75. Doctors thought that younger, more active patients would put too much stress on the joint and require a second artificial joint in 10 to 20 years; older patients were believed to be too frail to undergo the knee replacement procedure.
Over the past 20 years, however, researchers have concluded that knee replacement can be appropriate for people of almost any age. In 2003, a federal panel convened by the National Institutes of Health (NIH) determined that joint replacement provided pain relief and improved mobility in 90% of patients. The panel also suggested that, rather than being a last resort, knee replacement can be a valuable treatment option earlier in the course of arthritis.
Why Knee Replacement Is Often Delayed
Part of the reason that some patients wait a long time for knee replacement is that the decision is up to the individual surgeon, and there is no consensus as to the most appropriate time. Also, patients may be reluctant to undergo knee replacement for a variety of reasons: they don’t want to believe that their arthritis has become so serious; they fear the risks, pain, or cost associated with knee replacement surgery; or they worry about taking time off from work or caregiving.
The panel reported that women (and minorities) have knee replacement surgery less often than white men, even though women are more likely than men to have arthritis. Also, women who have a knee replacement have more pain and function loss than men at the time of the procedure, suggesting that either women or their doctors tend to delay surgery. However, these patients may be doing themselves more harm than good.
Why Earlier Knee Replacement May Be Better
Waiting until pain and function loss have become substantial may chip away at the potential benefits of knee replacement. For example, the NIH panel reported that after knee replacement, patients with worse pain and function scores before the procedure still had more pain and less function than people with better scores before the procedure. In a similar finding, a 2002 study of 222 people with osteoarthritis who underwent knee or hip replacement reported that those with poorer function at the time of surgery also had worse function two years after surgery, compared with people with less pain and better function before surgery.
One problem with waiting too long for knee replacement is that bone as well as cartilage may be worn away, making the procedure more difficult. Also, being disabled for an extended period can affect the muscles and make rehabilitation more difficult. Increased age may also be correlated with an increased risk of surgical complications from knee replacement.
Another factor in favor of earlier joint replacement is improved materials used in the artificial joint and refined surgical techniques. Both of these advances mean that younger patients are not likely to wear out the new joints, as was once feared. Ten years after knee replacement, only 10% of artificial joints are likely to need replacement; after 20 years, the rate is 20%.
According to the NIH panel, candidates for knee replacement should have:
- evidence on x-ray of joint damage
- moderate to severe persistent pain that is not relieved by measures such as medication or lifestyle changes
- significant functional limitation resulting in reduced quality of life
Conservative treatments—such as rest, ice, heat, muscle-strengthening exercises, and pain medication—should always be the first step in the treatment of knee arthritis. If these measures fail, however, knee replacement may be the best treatment option for many people.
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Posted in Arthritis on March 6, 2006
Reviewed May 2007
