For someone whose knee is sore and creaky, the prospect of replacing it with a new, metal-and-plastic version of the joint can be beguiling. The surgery seems so easy and to promise so much: better mobility, less pain, an approximation, almost, of youth. But there is growing evidence that knee-replacement surgery may be too seductive — and that many people considering the procedure would be better served to first try other ways to improve their knees.
There’s no doubt that knee replacements are increasingly popular. More than 600,000 such surgeries were performed in 2012, compared with about 250,000 just 15 years ago. But some new studies suggest that people may be electing to have the procedure prematurely and, perhaps worse, gaining limited benefit from it. According to figures from the American Academy of Orthopaedic Surgeons, the number of knee replacements in people between 45 and 64 soared by 205 percent between 2000 and 2012; among people 65 and older, the increase was only 95 percent.
For two major studies published this year, researchers at Virginia Commonwealth University in Richmond conducted a surgical-validity assessment. Using criteria developed in Europe, they concluded that knee replacements could be judged appropriate for only those whose arthritis in the knee was medically proven to be advanced. This means not just severe pain but also impaired physical function, like an inability to climb stairs, get out of a chair or walk without aid. Based on others’ work done in Spain, the researchers also determined that surgical replacements were better suited for patients older than 65. Their reasoning? The implanted materials wear out after a couple of decades, meaning a 45-year-old patient might need an additional knee replacement during his lifetime.
Researchers then analyzed the data from a large study of almost 200 men and women with aching, arthritic knees who went on to have replacement surgery within five years of entering the study. It turned out that approximately a third of the subjects would not have been regarded as appropriate candidates by the researchers. Many in this group had only slight arthritis, according to scans of their knees or the levels of their reported pain and physical impairment.
In a separate study, the same researchers also found that people who were good candidates for surgery — basically, they had really bad knees — benefited substantially from the surgery, reporting much less knee pain and much better physical functioning in the months immediately following the procedure and again two years later. On one commonly used measure of knee function, their scores improved by about 20 points on average. By contrast, subjects whose surgeries the scientists deemed inappropriate did not improve much. After a year, their scores on knee function had risen by only about two points.
“They had less room for improvement,” says Daniel Riddle, the professor of physical therapy and orthopedic surgery at Virginia Commonwealth University who led the studies.
The message is not that people should wait until their knees break down completely before replacing them. But they should question the need for surgery. “Ask your doctor how advanced your arthritis really is,” Dr. Riddle advises. If you do not have bone-on-bone arthritis, in which all of the cushioning cartilage in the knee is gone, think about consulting a physical therapist about exercise programs that could strengthen the joint, reducing pain and disability, Riddle says. Losing weight helps, too.
A version of this article appeared in the Nov. 16 issue of The New York Times Magazine.