Exercise Causes Joint Degeneration: Truth or Excuse?
“I want to start running, but bad knees run in my family,” my friend said as we stood chatting at the pool. “Both of my parents had knee replacements in their thirties,” she continued. Does strenuous exercise really cause joint degeneration? Or is the “running is bad for your knees” mantra an easy excuse?
If you’re a runner, you likely hear it at the table every Thanksgiving, “if you keep running you’re going to need knee replacements in your 40’s.” This usually comes from Uncle Bill, who spends most of his energy watching Netflix. He hasn’t exercised in decades because his “knees hurt from all that runnin’ he did as a kid.”
What would be interesting to hear from Uncle Bill is:
How does he know that his knees wouldn’t have hurt anyway? In fact, maybe all of that running he did when he was a kid actually made his knees better than they would have been otherwise. How does he know that his knees wouldn’t have been worse had he not run?
He doesn’t.
But scientists do. They have a tool to answer these questions called experimental research. With an experimental design, we can compare the effects on a person’s tendons and cartilage with and without strenuous exercise.
Here’s how:
Dr. Michael Kjaer, a Professor and Specialist in Rheumatology at the Institute of Sports Medicine in Copenhagen, Denmark, has carried out more than 200 studies examining the effects of exercise on joint health.
In one study, he recruited healthy males to examine how strenuous exercise would affect Patellar tendon (tendon of the knee) and quadriceps (thigh) muscles. Participants completed 1 hour of a one-legged kicking exercise at a relatively high (67% of max) intensity. In order to know whether changes in tendon and muscle strength were due to exercise exclusively, researchers had participants complete the kicking exercises on one leg, but not the other.
Then, they did a biopsy, meaning they removed a small piece of tissue from the tendon and muscles in each leg. Next, they compared post-exercise growth and damage between the exercised and the non-exercised legs.
The results showed that there was a rapid increase in collagen and protein synthesis after strenuous exercise in tendon and muscle tissue. This response is evidence that our bodies have a musculotendinous adaptation to strenuous exercise. Furthermore, there was no visible damage to the tendon or muscle.
What exactly does this mean?
Our bodies adapt to the demands placed upon them. When we run, lift weights, and do strenuous exercise, our muscles, bones, tendons, cartilage, and connective tissues become stronger. With exercise, our joints improve their ability to withstand greater forces.
More Research
Furthermore, research also shows that contrary to popular belief, running actually decreases risk of osteoarthritis and joint replacements. Instead of strenuous exercise causing degeneration, research shows that it’s really physical inactivity that causes the cartilage, muscles, and tendons to atrophy (i.e. decrease in size and strength).
Human joints do not deteriorate like a pair of old jeans with holes in the knees after years of wear and tear. Instead, as an adaptation to the impact of running, weightlifting, and exercise, our joints are like are more like a tree, that grows deep, strong roots when tested with wind and adverse weather conditions.
But you are an exception you say…
If you have joint injuries, you may be an exception, but not because you ran or exercised in your youth. Instead, research shows that joint degeneration is primarily genetic and obesity related. Additionally, collisions, falling on, and twisting of joints, as well as physical inactivity are all related to joint degeneration.
When progressively overloaded appropriately, exercise is the best thing that can be done for joint health.
The Caveat
Does this mean you should start running today? Maybe, maybe not. While research shows that running does not cause joint degeneration, it doesn’t mean that it’s safe or the best mode of exercise for everyone.
Running or any mode of exercise may be contraindicated depending on your body weight, current health or diseased state, and injury status. For example, exercising on an injured limb could make that injury worse. It is important to talk with your physician or physical therapist about the best mode and intensity of exercise for you before beginning exercise if you are injured. Your physical therapist can also prescribe modified exercises for you while your injuries heal. Really, there is no need to sit on the couch and passively wait for an injury to heal when there are alternative modes and modifications of exercise that you can do while you actively rest and rehabilitate your injury.
Therefore, to answer the original question: Is “exercise is bad for your knees” just an excuse? It is if you know the facts and continue not to exercise for that reason.
Thanks for reading! 🙂
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Reference:
Miller, B. F., Olesen, J. L., Hansen, M., Døssing, S., Crameri, R. M., Welling, R. J., … Rennie, M. J. (2005). Coordinated collagen and muscle protein synthesis in human patella tendon and quadriceps muscle after exercise. The Journal of Physiology, 567(Pt 3), 1021–1033. http://doi.org/10.1113/jphysiol.2005.093690
Williams, P. T. (2013). Effects of running and walking on osteoarthritis and hip replacement risk. Medicine & Science in Sports & Exercise.
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