Running Will (Not?) Ruin Your Knees!

It has been an oft-cited phrase, “running will ruin your knees”. On the face of it, it seems plausible. Most running is done in urban environments on concrete. Running is the act of jumping alternately from one foot to the other. Most recreational runners use a cadence of about 165 steps per minute, so in a typical 30-minute run, they would take about 5000 running steps per day. A marathon runner would take about 30,000 steps in a 3-hour weekend training run. Much of that impact coming down onto each foot and travelling up the leg goes into the knee joints. Surely that must cause wear and tear and ultimately knee degeneration, right? The weight of evidence says no, it does not.

In an on-line interview about her group’s research, Grace Hsiao-Wei Lo, MD, from the Baylor College of Medicine in Houston said “In people who do not have knee osteoarthritis, there is no reason to restrict participation in habitual running at any time in life for fear that it will be harmful to the knee joint. “
Her research group looked at non-elite recreational distance runners. Dr. Lo and her colleagues assessed 2683 participants. Average age was 64.5 years, mean body mass index was 28.6 kg/m², and 56% of participants were female. The 29% of participants who had run at some point in their lives were classified as runners.
In all age groups, the prevalence of knee pain was lower in runners than in nonrunners (35.0% vs 41.6%), as was the prevalence osteoarthritis that showed up on X – ray (53.7% vs 60.3%) and symptoms of osteoarthritis (22.8% vs 29.8%). Results were similar after adjustment for age, sex, and body mass index.
It should be noted that runners are generally thinner and eat a better diet than non- runners. That could affect the study results because increased weight has been shown to increase the risk of knee and hip degeneration.

In another study, Australian researchers reviewed multiple studies covering several decades. The participants in those studies were runners and people who took part in other running-related sports (e.g. soccer, basketball) . What they found was that active people had no more joint – space narrowing in their knees than non – runners. Joint space narrowing is assessed on x-ray. If two bones that meet at a joint are too close together on an x-ray, that means the cartilage ( nature’s shock absorber) is degenerating and getting thinner. This is often the first marker of osteoarthritis. So this research found that active people and runners had no increased frequency of early signs of knee osteoarthritis.
A final piece of evidence, in 2008 from Stanford University, followed middle-aged, longtime distance runners for nearly 20 years, beginning in 1984, when most were in their 50s or 60s. At that time, 6.7 percent of the runners had mildly arthritic knees, but none of an age-matched control group did. After 20 years, however, the runners’ knees were healthier; only 20 percent showed arthritic changes, versus 32 percent of the control group’s knees.

So what is at work here? What is happening is that we are biological and not automotive! You drive your car for 20 years and it gets worn down and rusty. However, if you run (or exercise with weight-bearing activities) your body undergoes small microscopic injuries to the cartilage. The body repairs these little insults to the tissue as you rest afterwards. But it doesn’t just rebuild it, it builds it back even better than it was before. By running you are telling your body that it needs to be strong and resilient for your next run. Over years, you build strong cartilage and leg muscles which acts to absorb shock and reduce the chance of you getting knee osteo-arthritis and degeneration. If you have been using the old “running will ruin your knees” mantra, it is time to let it go, put your shoes on and head out the door.