Most people think that osteoarthritis is simply due to “wear and tear” of the joints, and therefore that running would put you at a higher risk, but this is (fortunately) not correct. Runners develop less knee osteoarthritis than the general population and if they do, they usually suffer less from it.
What is it?
Osteoarthritis occurs when the normal breakdown and repair of joint tissues becomes unbalanced. It affects the whole joint, even though osteophytes (bone overgrowth) and thinning of the cartilage are the best known signs. It can cause severe pains, but many persons with clear signs of osteoarthritis on radiographs are just fine.
Osteoarthritis can be caused or aggravated by a long list of problems, such as joint infections and genes, and it is still a badly understood disease. In this post we will concentrate on the relationship between running and knee osteoarthritis in people with no underlying problems.
Many people believe that osteoarthritis is caused by the gradual thinning of the cartilage due to repeated pounding. However, the main shock absorbers are the properly contracting muscles, and therefore exercise can protect the joints. Moving and loading your joints will also stimulate the cells in your cartilage and keep them healthy.
Your muscles can only contract properly if your joint is stable and well aligned.
Injuries to joint structures, such as ligaments and menisci, are well-known risk factors. There are three ways by which they can lead to osteoarthritis. Firstly, the cartilage can be damaged at the time of the injury and osteoarthritis develops over the years. Secondly, the joint becomes unstable which leads to recurrent cartilage damage. Finally, the muscles do not work properly anymore and therefore they cannot absorb the impact forces appropriately, which results in cartilage damage.
Studies have shown that small amounts of misalignment (bowl-legged or knocked-knees) lead to big differences in force distribution in the joints, and increase your risk.
You could consider improper running technique as a form of misalignment, but as yet we do not know what its effect is, even though experts suppose it is important.
Being obese or overweight puts you at a higher risk of knee osteoarthritis, but it is not sure if overweight people who exercise increase their risk further.
In 2007, Dr Wang showed that the risk was linked to the amount of fatty tissue, and not to BMI. Fatty tissue produces adipokines, which behave like hormones. If you have too much visceral fat, the adipokine production becomes disturbed and Dr Wang thinks that this puts you at risk. If this is true, running should reduce your risk, as it makes you lose visceral fat even if you do not lose weight.
What do we see in practice?
There is agreement between researchers that recreational running does not increase your risks, even if you are running long distances, as long as you do not have an injury and your muscles are strong enough.
Theoretically though, running should have a favourable effect. Although some studies show this, others do not. This might be due to the fact that they are so difficult to conduct. They usually rely on questionnaires to determine how physically active the participants are, and how much they suffer from osteoarthritis. People might overreport their training and over- or under-report their symptoms non-intentionally. Radiographic assessment is hampered by issues of measurement and interpretation, and there is not always a good correlation between the radiographic signs and the symptoms. Moreover, the professional occupations of the participants are not always taken into account, although heavy physical work is an important risk factor.
How many people have ever tried to warn you that you are destroying your knees by running? If only they knew…
Disclaimer: this article is for general information only, and does not replace medical advice. It cannot be used to diagnose or guide treatment. If you have any concerns or questions, you should talk to a qualified health provider.
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