Women with strong thigh muscles are less likely to get painful knee arthritis in later life, a study suggests.

What do we know already?

Many older people get arthritis in their knees. It can be painful and makes it hard for people to get around and live a full life. Doctors are interested in finding out why some people get symptoms of knee arthritis and others do not. It doesn’t seem to be just about wear and tear; some people’s knees show signs of damage on X-ray, but it doesn’t cause them pain.

Previous studies have found that people with knee arthritis have weaker leg muscles than other people. But it’s hard to tell whether that’s a cause of arthritis, or a consequence. People with painful arthritis tend to walk and exercise less, so their muscles are likely to get weaker.

In this new study, people aged over 50 without pain from knee arthritis or signs of arthritis on X-ray had their leg muscle strength tested. They were followed up for an average of two and a half years, then asked again about knee pain and had another knee x-ray. People whose knees were painful and showed signs of damage on X-ray were diagnosed with symptomatic (painful) knee arthritis.

What does the new study say?

The researchers tested the strength of the quadriceps muscle, at the front of the thigh. They found that women with the strongest thigh muscles at the start of the study were less likely to get arthritis pain. Thigh muscle strength had some effect on men’s chances of developing painful knee arthritis, but the difference was so small that it might have been down to chance. About 10 percent of women and 8 percent of men got painful knee arthritis during the study.

Interestingly, thigh muscle strength made no difference to the likelihood of people’s knees showing arthritis damage on X-ray, without pain.

How reliable are the findings?

The study looked at more than 2000 people. It seems to have been carefully carried out. However, it’s unclear how significant the results are in practice.

Some of the people in the study had knee pain at the start of the study, even though their knees didn’t show signs of damage on X-ray at this point. So their muscle strength might have been affected by the pain, rather than the other way round.

Where does the study come from?

The study was carried out by researchers from a number of US universities. It was published in the medical journal Arthritis Care and Research. The study was paid for by US government grants and the Association of Academic Physiatrists.

What does this mean for me?

There are lots of good reasons for keeping active and taking exercise as you get older. These reasons include keeping your heart healthy and possibly cutting your chances of memory and thinking problems such as dementia. This study suggests that keeping your thigh muscles strong might also help to avoid painful knee arthritis.

What should I do now?

Keeping active is important for health at any age. Even if you already have arthritis, previous research has shown that exercise can help to control pain and keep you mobile. If you want to start an exercise programme but you’re older and not sure where to start, your GP can advise you on what’s suitable for you.

From:

Segal NA, Torner JC, Felson D, et al. Effect of thigh strength on incident radiographic and symptomatic knee osteoarthritis in a longitudinal cohort. Arthritis Care & Research. Published online 27 August 2009.

To find out more about what causes arthritis, and how it can be treated, see our information on osteoarthritis.

© BMJ Publishing Group Limited (”BMJ Group”) 2009

http://www.guardian.co.uk/lifeandstyle/besttreatments/2009/aug/27/women-with-strong-thigh-muscles-have-less-chance-of-arthritis