Run to Please Your Knees

Quick facts: 

  1. Long distance running is not associated with acceleration of osteoarthritis in healthy older adults
  2. Short term study demonstrates that 30 min of running will lower markers of inflammation in your knee while 30 min of sitting will increase markers of inflammation in your knees

When you feel that faint tug on your kneecap as you descend a set of stairs after a challenging run, are you haunted by that whisper in your ear, “running is bad for your knees?” As an ultra runner and physical therapist, that voice in my head has been strengthened by numerous friends, family members, and even patients who try to warn me that I’ll be facing a world of pain when I’m older if I keep up this “crazy running” thing.

My reply is generally two fold: 

  1. I am making an educated decision to run now and suffer later. 
  2. By the time my knees wear away, science will have progressed significantly and knee replacement rehab will no longer be a lengthy and painful experience (spoiler alert, it currently is). 

Well, fortunately and unfortunately (who likes to be wrong?), I have been responding incorrectly. My “educated decision” did not include new evidence that has emerged indicating that not only is running not related to knee osteoarthitis, it may actually be protective for your knees. 

 

Here’s the old thought process: Running involves a lot of pounding, pounding causes damage, therefore, by the transitive property, running causes damage. Don’t worry, I’m not making an argument against the transitive property (it’s maybe the only part of geometry that I remember from Mr. Lindahl so I’m holding onto it), I’m just no longer convinced that pounding causes damage. 

“Damage” or degradation of the cartilage in your knee leads to osteoarthritis. Signs of osteoarthritis can be determined by a few different mechanisms, two of them being the level of cytokines and COMP in your synovial fluid. Okay, okay, let’s back up and define. Your synovial fluid is the fluid inside all of your joints that provides nutritional support for your cartilage and reduces friction. This synovial fluid contains COMP or cartilage oligomeric matrix protein that is a marker for worsening osteoarthritis. This fluid also contains cytokines which are proteins secreted by the immune system that are a sign of inflammation, which is chronically high in patients with osteoarthritis. Basically, high levels of COMP and cytokines are bad news for your knees.

 

Based on the old thought process, one would expect that runners have relatively higher amounts of COMP and cytokines in their knee joint synovial fluid because people assume that running causes osteoarthritis. However, a new study conducted out of Provo, Utah looked at these two proteins, COMP and cytokines, in volunteers after they had been sitting for 30 minutes or running for thirty minutes. To the glee of all runners, this study found that the levels were HIGHER than baseline in the volunteers after they had been sitting and LOWER than baseline values after they had been running. 

 

Therefore, running may actually protect your knees from osteoarthritis.

Before you text an “I told you so” to all of those NARPs (non-athletic regular person) who have ever questioned your running obsession as you throw on your running shoes and race out the door, here are a few things to keep in mind: 

  1. This study was able to obtain quality data from only 6 volunteers. In research world, that’s a VERY low number so caution should be heeded when applying this information. 
  2. The variables consisted of only 30 min of either sitting or running so be careful when extrapolating this data to longer periods of running. You know what happens when you assume…

 

While no other studies solve these issues with analysis of COMP and cytokine levels, luckily, these are not the only scientists who have studied osteoarthritis and running. An article from 2009 looked at long-distance runners over the age of 50 who had already been running for about a decade and matched them with similarly aged participants who did not run. After Xraying these folks every few years for the next decade, there was no difference in the acceleration, prevalence, or severity of osteoarthritis between those who ran and those who didn’t. In fact, the only knee replacements that were performed between these 98 participants were non runners. PLEASE do not infer from that statement that no runner will ever require a knee replacement. 

Other grains of salt regarding that study include that the runners group had a lower BMI (higher BMI is associated with increased risk of osteoarthritis), were slightly younger, and had a greater prevalence of prior knee injuries. While all of these values were statistically non-significant, (i.e. age of runners: 59.8 vs age of controls: 60.2), they should be kept in mind. Another key quality of the study to consider is that osteoarthritis was determined through radiographic imaging, yet we have a ton of evidence that demonstrates that Xrays do not always correlate with symptoms. Just because a runner’s Xray doesn’t look too shabby, doesn’t mean that runner is pain free in the knees. 

While, as always, more studies should be conducted to look at the long term effect of running on knee OA, I’ll leave you with some statements from oldie but goodie articles:

“Our observations suggest, within the limits of our study, that long-duration, high-mileage running need not be associated with premature degenerative joint disease in the lower extremities” 

And 

“In sum, habitual physical activity does not increase the risk of knee OA for men or women.” 

I’ll make sure to hear these voices in my head next time my knee complains on a stair 🙂