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Release suggests running can reduce knee inflammation but a study of just 6 volunteers is far too small to draw a conclusion

Study: Running actually lowers inflammation in knee joints

Our Review Summary

running, kneesThis news release suggests that long distance running may be protective of knee cartilage because the amounts of two biomarkers for synovial fluid inflammation decreased after 30 minutes of running. The volunteers in the study were all under 35 and healthy. Similar subjects tested without running showed no decrease in the two markers.

The release does a poor job of conveying the findings and will leave readers with the impression that this research is much more definitive than it really is. Here are a few of the shortcomings:

  • The release doesn’t say how much the markers decreased and whether that difference would be expected to make a meaningful impact on inflammation levels.
  • It does not caution readers about the many limitations of this research or attempt to place it in context. For example, how does this study compare with other research looking at actual rates of arthritis in runners compared with non-runners? And can measuring a couple of biomarkers after a single 30-minute run really tell us anything about the impact of running over a lifetime?
  • It does not notify readers that this was a pilot study and that functionally, only 6 subjects are included in the results.  Not a statistically acceptable number.


Why This Matters

Patients who suffer joint inflammation are often told to quit running, but if running is beneficial for knee inflammation, then discontinuing this exercise may be unnecessary. This news release makes it sound as if this is the first study to ever address this issue and that the results definitively indicate that running is protective against the development of knee arthritis. But that’s very misleading. In fact, many other studies have looked at this question and come back with conflicting findings. This new study, of only 6 people, is low in quality and adds little to the evidence base. It probably did not deserve a news release at all, no less one that overstates the findings as as carelessly as this one.


Does the news release adequately discuss the costs of the intervention?

Not Applicable

There is no cost mentioned, but typically, running does not have any cost requirement except for good shoes. This category is not applicable for this research.

Does the news release adequately quantify the benefits of the treatment/test/product/procedure?

Not Satisfactory

The benefits of this approach are in no way quantified. The news release states that the amounts of inflammation markers decreased, but does not say by how much although the published study includes this information. It should be kept in mind that the inflammation markers are a proxy for what we really care about — actual rates of osteoarthritis. It is doubtful that measuring two biomarkers after a 30-minute run can tell us much about the impact of running over a lifetime.

In addition, the release does not mention that this is a pilot study and that only 11 subjects were used and only 6 actually completed the tests because synovial fluid is difficult to obtain from a healthy joint. The paper does include statistics, but the p values (the probability of obtaining a result equal to or exceeding what was actually observed) may not be of any use when applied to only 6 subjects. This does not seem to be a statistically valid study. The release was probably premature.

Does the news release adequately explain/quantify the harms of the intervention?

Not Satisfactory

Possible harms are not discussed. The release hints that this benefit is there for “healthy” joints, but says nothing about joints with torn cartilage, already degrading joint surfaces or substantial osteoarthritis. The release notes that researchers plan more do more study of those with anterior cruciate ligament (ACL) injuries, but that is a tendon injury, not a joint injury.

There’s a concern that this release could send the wrong message to some runners. What about people who experience pain when they run? Should they continue to run, despite the pain, because running might be “chondroprotective.”

Does the news release seem to grasp the quality of the evidence?

Not Satisfactory

With only 6 successful subjects, the quality of evidence is lousy. But the release doesn’t comment on this at all or discuss any limitations of the study. It doesn’t even tell us how many subjects there were.

Does the news release commit disease-mongering?


The release doesn’t engage in disease mongering. Osteoarthritis in the knees and other joints is a factor of aging.  Anything that can prevent this occurrence is of benefit.

Does the news release identify funding sources & disclose conflicts of interest?

Not Satisfactory

There is no funding source listed, but there is also no funding source listed in the paper.  The authors do declare in the paper that there is no conflict of interest and what any conflict would be, considering that the “treatment” discussed is running, is a puzzle.

Our standard here is to require some discussion of funding sources. Even if no funding was provided, the release should say so.

Does the news release compare the new approach with existing alternatives?

Not Satisfactory

There is no mention of any alternatives. Many runners are told to switch to other forms of exercise as they get older to avoid joint pain. Do other forms of exercise produce the same benefits on inflammation?

Does the news release establish the availability of the treatment/test/product/procedure?

Not Applicable

Obviously, running is available to anyone who’s able to do it for no cost. The release could have pointed out that areas with sidewalks and dedicated trails make this activity more accessible.

Does the news release establish the true novelty of the approach?

Not Satisfactory

As stated in the review summary, many previous studies tried to determine whether running increases the risk of osteoarthritis. But the release doesn’t mention previous research and thus overstates the novelty of the new findings.

People with osteoarthritis are usually advised to continue to exercise. Because running is a high impact aerobic exercise it may sound counter-intuitive to continue running, but not necessarily novel.

Does the news release include unjustifiable, sensational language, including in the quotes of researchers?


The release doesn’t include unjustifiable, sensational language. However, the focus on a study with functionally only 6 subjects isn’t at all as revealing as the headline suggests.

It reads: “Running may also slow the process that leads to osteoarthritis.” That’s confusing. Besides slowing the process, what does running do?

Total Score: 2 of 8 Satisfactory


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