Conventional wisdom has been that running is bad for your knees and hips, and that patients with knee and hip osteoarthritis should refrain from running and switch their activity program to other forms of low impact exercise. That conventional wisdom has recently being challenged by several medical studies that have found that running not only doesn’t increase your risk of developing leg osteoarthritis, but that it may even prevent the condition.
A new study coming from Baylor College of Medicine (where I used to teach) analyzed data from 2,683 subjects as part of a long term study. Looking at self-described activities and knee x-ray information from that pool of subjects they found that the percentage of subjects with knee osteoarthritis was 22.8 % for runners as compared to 29.8% for those who had never been runners. This is in agreement with previous studies, like this one, showing that long distance running among older individuals was not associated with increased incidence of knee osteoarthritis.
But, how about the hip? The results seem to be the same. Another large study, published about 2 years ago, looking at almost 75,000 runners and 15,000 walkers, had already reported that running significantly reduced the risk of hip osteoarthritis and hip replacement surgery.
If, at first, it sounds contradictory that running, which imposes high peak loading forces to the joints of the legs is not associated with higher incidence of osteoarthritis of those joints, this study from Canada may offer a reasonable biomechanical explanation. The researchers had normal subjects walk and run in their lab while measuring the forces created, how often, and for how long. They found that the load the joints were subjected to, over a given distance, was the same, regardless of whether the subjects ran, or walk. When we run, our legs pound the ground with more force, but, we take longer strides able to cover the same distance hitting the ground fewer times, and also for a shorter amount of time. It seems that the combination of longer strides (we cover more ground with each step) and shorter contact time between ground and foot, blunt the effect of higher peak loading forces on the joint when we run. So, the end-result is that the per unit distance load (the load we place on the joints to cover a certain distance) is not higher in running than in walking.
In summary, if you are a runner and you have osteoarthritis, and your doctor advises you to stop running, you may be receiving outdated advice. Running does not predisposes you to more arthritis, and it possibly even protects your joints. However, if you are not a runner, or you used to be, and are overweight, you may want to lose your extra weight before you start/resume a running program.
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