Light exercise may prevent osteoarthritis

29^th November 2010 - Light exercises such as walking and bowling, and avoidance of knee-bending activities such as climbing and squatting, may protect against osteoarthritis of the knee in at-risk people, researchers report.

However, high-impact sports such as running and skiing are associated with knee cartilage damage in people who are overweight, have had knee injuries or knee surgery, have a family history of osteoarthritis, or have other risk factors, according to a study presented in Chicago at the annual meeting of the Radiological Society of North America (RSNA).

Osteoarthritis is a degenerative joint disease that causes pain, swelling, and stiffness. Osteoarthritis is the most common type of arthritis in the UK. Around one million people see their GP about it every year.

Analysing activity levels

The new study involved 132 people at risk for knee osteoarthritis who were enrolled in the US National Institutes of Health Osteoarthritis Initiative, as well as 33 people of similar ages and weight who were not at risk. Participants included 99 women and 66 men aged 45 to 55.

The researchers, led by Keegan Hovis, RN, of the University of California, separated participants into three exercise levels:

• Sedentary: watching TV, reading, or other sitting activities more than two hours a day, two or more days a week
• Light exercisers: walking, playing darts, Frisbee or other light activities two or more hours a day, three or more days a week
• Moderate to strenuous exercisers: running, cycling or other moderate to strenuous sport more than an hour a day, three or more days a week

Knee-bending activities such as climbing, kneeling, and lifting heavy objects were also analysed.

Virtues of light exercise

Among people with osteoarthritis risk factors, MRI scans showed that light exercisers had the least amount of cartilage damage.

"It can be postulated that light exercise is protective against osteoarthritis" in these individuals, Hovis tells us.

The scans also showed that women with osteoarthritis risk factors who fell into the moderate-to-strenuous exercise category had substantially more cartilage degeneration in their knees than any other group.

Asked why men were not affected similarly, Hovis says that's unknown. "But women overall are at greater risk for osteoarthritis than men."

Among people who were not at risk of osteoarthritis, the exercise level did not affect cartilage degeneration.

However, frequent knee bending - climbing 10 or more flights of stairs per day or kneeling for 30 or more minutes a day, for example - was associated with more damaged cartilage in people with and without osteoarthritis risk factors.

Risks of aggressive exercise

Researcher Dr Thomas Link, chief of musculoskeletal imaging at the University of California, tells us that cartilage doesn't regrow.

"We're not saying you shouldn't run or climb stairs. But you have to be extremely careful to protect your cartilage starting at a very early age," before you reach 40 or 50, he says.

The research fits with NHS advice to do regular exercise to look after joints, while not putting excessive strain on them. It also recommends keeping muscles strong with 30 minutes of exercise five times a week. If you are overweight or obese, this can make osteoarthritis worse - so losing excess weight and then maintaining a healthy weight is advised.