The Impact of Running on Your Knees

Science says running may in fact provide protective benefits to the knees of some people.

By Bert Mandelbaum, MD

Orthopaedic, Sports Medicine
Member, Cedars-Sinai Kerlan-Jobe Institute Board of Directors
Co-Chair of Medical Affairs, Cedars-Sinai Kerlan-Jobe Institute
Director, FIFA Medical Centre of Excellence in Santa Monica
Team Physician, US Soccer National Teams

When it comes to the myriad of health and fitness myths floating around, the notion that “running wrecks your knees” is one that is commonly held. Most people generally agree that it’s a fantastic workout with many a heart-health benefits, but they might also believe that the repetitive footfalls on a hard surface will destroy their knees long before their hearts give out. It’s understandable. There’s even an orthopedic condition frequently referred to as “runner’s knee,” so there’s got to be truth to some of it, right? Well, if concerns about potential damage to your knees are why you’re not taking up running or you’ve gone cold turkey; some recent scientific news may restore your hope (or give you an excuse to cross off the list.)

Recently, researchers looked into the effects of running on the intra-articular and circulating markers of inflammation and cartilage turnover in otherwise healthy people. There’s a mouthful of medical terminology in that last sentence so let’s break it down a bit. First, the researchers used healthy subjects for their study because they wanted to find a way to isolate the specific effects of running on the knees. All subjects in the study were either instructed to run for 30 minutes or to sit for the same amount of time and blood, and knee fluid samples were taken from each of them after these activities. From these samples, the researchers were looking for cells that are associated with knee inflammation, as previous research has shown that these cell types contribute to the development of knee arthritis. Upon examination of the samples in nearly every case, the knees of the runners showed much lower levels of the inflammatory and arthritis-marker cells. But something unexpected also came out of this research. For those subjects who were seated during the 30 minutes and not asked to run, the cells in their knees changed too – and not for the better. From a biochemical perspective, the fluid samples from the knees of these individuals indicated that they might be more vulnerable to arthritis later on.

You may be wondering how this is all possible, especially if you’ve consistently heard about how running is a knee-killer. It’s an interesting question. How can repeatedly pounding on the knee joints indeed make them healthier? Here’s an example of one way to think of it: take weight-bearing exercise as an example. Science has shown that lifting weights indeed increases both muscle and bone mass, making them stronger over time. What happens during a weightlifting session is that the muscles undergo thousands of minuscule tears in their fibers which then regenerate and repair themselves. All the while, the tissue is building more mass and becoming stronger and healthier in the process. The concept is similar to the structures that make up the knee joint. The impact of body weight on the knee joints during a run seems to prompt the cartilage in the knee to repair minor damages while simultaneously releasing certain chemicals in the cartilage that help to strengthen it.

Of course, this research doesn’t aim to suggest that you’ll never sustain an injury while running. This particular study looked at young (under 30) and healthy individuals and at consistent jogging or running as a potential promoter of long-term joint health. For those who don’t fit into the general “young and healthy” mold, all hope is not lost. You’ll just want to consider some things if you decide to take up running. First, if you have suffered any significant knee injury, especially if it required surgical repair, this could be a caution sign for you because the knee joints may not have the fullest working capacity they once did. Running caution should also be taken by those who are 20 pounds or more overweight. Running with extra body weight stress on the joints significantly increases the risk of knee inflammation and damage. For people who are interested in running but are overweight, it’s best to first lose the extra weight by non-weight-bearing exercises until the body weight reaches a point that is safe for the joints to support. If either of these scenarios describes you, make sure you talk to your doctor before beginning any new exercise or running routines.

Armed with emerging research that favors running as protective for the knee joints, it seems that the old way of thinking about running is a thing of the past. So feel free to (depending on your physical health) lace up the running shoes, hit the road, and give those knees something to be happy about!


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