Many people think of arthritis as a disease of old age. But increasingly, painful symptoms of arthritis, especially of the knees, are afflicting us in middle age. And the problem is getting worse, in large part because of the excess weight we're carrying around.
Osteoarthritis, the most common type of arthritis, is a chronic, degenerative joint disease. As we age, the cartilage between our joints wears out. By age 40, 90 percent of people have x-ray evidence of osteoarthritis, according to Johns Hopkins Health Alerts, although most will not yet have symptoms of the disease.
A 2008 symposium of the American Academy of Orthopaedic Surgeons focused on the growing trend of knee arthritis in people in their 40s and 50s. Knee arthritis is especially common in people with a high body mass index (BMI). "A significant portion of people in the 50- to 70-year-old baby boomer range have BMIs that are greater than 30, which is outside the healthy range. Evidence shows that around 20 percent of those people will develop knee arthritis," said John J. Callaghan, MD.
Another study found a dramatically higher risk of knee arthritis, especially for those who are overweight. Researchers from the Centers for Disease Control and Prevention and the University of North Carolina followed more than 3000 people in Johnston County, North Carolina, for two decades. Participants were extensively interviewed and given a series of medical tests, including x-rays of hips, knees, spine and hands.
The study found that race, sex and educational levels did not play a role in whether people got arthritis of the knee. But being overweight was a significant factor. Those who were of healthy weight had a 30 percent lifetime risk of getting knee arthritis — that number jumped to 60 percent for people who were overweight or obese.
According to the Arthritis Foundation, for every pound you gain, your knees gain three pounds of added stress. For your hips, every pound adds six times the pressure.
Genetics also play a role. Some people may inherit a gene that affects their body's ability to produce collagen, a protein in cartilage. Our genetic inheritance may also influence the way our bones and joints fit together, with some people experiencing more wear and tear.
If you have to do a lot of bending and lifting in your work — for example, landscaping or carpentry — you also may be at greater risk of getting knee arthritis.
If you have osteoarthritis, you can download a free guide to pain relief, written by the editors of Johns Hopkins Health Alerts.
