“The heavier you are, the more likely you are to get osteoarthritis,” explains David Felson, professor of medicine and epidemiology at the Boston University School of Medicine.
Osteoarthritis is caused by the breakdown of cartilage, which can lead to pain and stiffness in the knees, hips, and other joints. (It is a different disease than rheumatoid arthritis, an autoimmune condition in which the body attacks the lining of the joints.)
When researchers in Norway tracked more than 1,600 people with healthy knees for 10 years, those who were overweight or obese were two to three times more likely to be diagnosed with osteoarthritis of the knee than those who were normal weight.
Among the ways that weight can damage your joints:
Load. “Every extra pound increases the stress across the knee joint three to five times,” says Roland Moskowitz. “So you’re increasing your risk of osteoarthritis many times by being overweight.” Moskowitz is clinical professor of medicine at University Hospitals Case Medical Center in Cleveland.
Injury. “In addition to the extra stress on the joints, being overweight may increase the risk of injuring the joints, which can lead to osteoarthritis,” notes Carrie Karvonen-Gutierrez, an assistant research professor at the University of Michigan School of Public Health.
In one study, 500 people who were having surgery to repair a torn meniscus were about three times more likely to be overweight than to be normal weight. (The meniscus is the cartilage that helps your knees absorb and distribute weight across the joint.)
“People with small meniscal tears tend to be at very high risk for getting osteoarthritis later,” notes Felson.
Inflammation. “We now know that fat cells release inflammatory chemicals that can break down cartilage,” says Karvonen-Gutierrez. Increased inflammation throughout the body might explain why some people get arthritis in the hands, which aren’t weight bearing.
“Obesity is the number-one risk factor for osteoarthritis, one that’s preventable and modifiable,” says Karvonen-Gutierrez. “So weight loss is really important.”
Shedding pounds is also important if you have arthritis. In four trials involving a total of more than 450 overweight or obese adults with osteoarthritis of the knee, those who lost at least 5 percent of their body weight reported less physical disability.
In the largest of the four studies, 76 overweight or obese adults aged 60 and older who lost an average of 11 pounds over 18 months reported 24 percent better knee function than 78 similar people who were told that a healthy lifestyle is important, but who didn’t lose any weight. (Better function means, among other things, greater range of motion, better ability to bear weight, and an easier time climbing stairs.) The weight-losers also reported feeling 30 percent less pain.
Sources: BMC Musculoskelet. Disord. 2008. doi:10.1186/1471-2474-9-132; Am. J. Prev. Med. 28: 364, 2005; Ann. Rheum. Dis. 66: 433, 2007; Arthritis Rheum. 50: 1501, 2004.
Other relevant links:
- Does glucosamine help alleviate pain? See: Glucosamine and Arthritis
- Eat fatty fish to get a good dose of DHA. See: DHA and Arthritis
- What is the impact of consuming milk on arthritis progression? See: How to Diet: Is Drinking Milk Good for Your Knees?