Kate Wright
Arthritis in the knees is a preventable disease rather than an inevitable consequence of wear and ageing, a study has concluded.
The condition is twice as common today as it was before the Second World War, according to researchers who put the increase down to lifestyle changes such as diet or footwear, as well as people getting fatter and living longer.
Osteoarthritis is a painful disease of the joints, affecting 8.8 million people in Britain aged above 45. More than 18 per cent of this group have the disorder in their knees. Yet scientists who studied more than 2,500 skeletons, from prehistoric hunter-gatherers to the present, discovered that rates of osteoarthritis had surged over the past few decades after centuries of stability.
Daniel Lieberman, professor of biological sciences at Harvard University and a senior author of the paper, said that many cases could be averted if doctors could determine what had driven the change over the past 70 years. The researchers are investigating whether factors such as physical inactivity, diets loaded with refined sugars, the shoes we wear and even the hardness of pavements could lie behind the increase.
“Knee osteoarthritis is not a necessary consequence of old age,” Professor Lieberman said. “We should think of this as a partly preventable disease. Wouldn’t it be great if people could live to be 60, 70 or 80 and never get knee osteoarthritis in the first place? Right now, our society is barely focusing on prevention . . . so we need to redirect more interest toward preventing this and other so-called diseases of ageing.”
In osteoarthritis, the cartilage protecting the ends of bones gets rougher and thinner, leading to changes in the joint tissues. Eventually, if the cartilage wears so thin that it no longer covers the ends of the bones, they rub against each other, heightening pain, changing the shape of the joint and shifting the bones out of position. Three quarters of those with osteoarthritis say that they are in constant pain. Treatment is generally limited to painkillers or steroid injections into the joint. For severe cases, the only further option is an artificial joint. In 2015 people with the condition accounted for 98 per cent of patients having a first knee replacement.
Ian Wallace, the study’s lead author, visited collections of human remains across the United States to look for the glass-like polish that the condition leaves on the thigh and shin bones over years of rubbing against each other. Rates of knee osteoarthritis among the over-50s appear hardly to have changed between the native Americans 3,000 years ago and the inhabitants of Ohio and Missouri in the first half of the 20th century. After the war, however, they more than doubled. The trend, set out in the journal PNAS, remained even after the researchers corrected for age and body-mass index.
“There are probably a lot of contributing factors,” Dr Wallace said, “but . . . two conspicuous ones are physical inactivity and the abundance of proinflammatory foods in our diet — especially really sugary things.”
Philip Conaghan, professor of musculoskeletal medicine and a spokesman for the charity Arthritis Research UK, welcomed the study. “The more we know about what causes it, the closer we will be to finding more effective treatments and even a cure,” he said. “We absolutely agree that there should be more focus on prevention.”
How to keep healthy knees
- Exercise regularly, both to strengthen your muscles and to maintain aerobic fitness. But don’t overdo it: if your joints are swollen or painful, rest them before exercising again
- Maintain a healthy weight, or lose weight if you are too heavy. Extra weight increases the stress on your joints
- Avoid repetitive motions that are tough on your joints, such as excessive kneeling, twisting, or lifting
- Regulate your blood sugar levels if you have diabetes. Research has implicated diabetes as a risk factor for osteoarthritis
