Knee arthritis rates have spiked, and researchers don’t know why
knee osteoarthritis, a painful and disabling condition in which cartilage wears down and bones rub against each other, have doubled in the past 50 years, according to new research. The cause of this spike is a mystery—which raises the tantalizing possibility that when the triggers are found, the pain can be stopped.
Ian Wallace, a paleoanthropologist at Harvard University, and colleagues examined several thousand skeletons of people who died during three eras in America: pre-industrial (300 to 6,000 years ago), early industrial (1800s to early 1900s) and post-industrial (late 1950s onward), tallying cases of knee osteoarthritis in each group. They also noted the age and body mass index of the cadavers, when available.
According to the study, reported August 14 in Proceedings of the National Academy of Sciences, 18 percent of the skeletons from the post-industrial period had signs of advanced knee arthritis, versus up to 8 percent of the older bones. The disease was more than twice as common among modern bones compared with either of the older two.
The primary risk factors for knee osteoarthritis were long thought to be aging and obesity, but researchers found no statistical relationship between either factor and the rise in arthritis. Even among skeletons of similar ages and weights from the different eras, knee arthritis was more common among the post-industrial skeletons. Some unknown cause or causes must be at play.
Identifying those missing risk factors could lead to better prevention and reduced arthritis prevalence, Wallace says.
Study co-author David Felson, a physician at Boston University, says physical inactivity likely plays a part. “Our joints don’t do well when they aren’t active much of the time.” Inflammation due to hypertension or diabetes could contribute, says Francis Berenbaum, a physician at Pierre & Marie Curie University. A diet high in processed sugars and grains may also lead to inflammationdriven arthritis, says Wallace.
The results suggest arthritis may not be “an inevitable aspect of aging,” Wallace says. That’s the good news behind the bad news here.