To Run or Not to Run?

Juan Francisco Lladó Sabater / CC BY-NC-SA 2.0

Like millions of other Americans, I love to run. I do it for exercise, yes, but also because I just can’t stop. The endorphin buzz of a good run is almost impossible to describe. It gets me outside in Chicago winters, in the rain, and after 30-hour overnight shifts. The only problem is the incessant nagging about impending knee destruction from the non-runners in my social circle.

This issue was discussed in a blog entry at the New York Times last week, and quickly became one of the most emailed articles of the day.

Until recently, I assumed the critics were right. It seems logical, after all, that the repeated impact of even a casual run would put stress on the knee joint. But it turns out that the connection between running and arthritis of the knees might not be as solid as most of us think. While elite athletes do have an increased risk of lower extremity injury secondary to their training, what about casual athletic activity? Does the connection still hold?

My curiosity was piqued after reading the Times commentary, so I went back to the scientific literature and started evaluating additional studies. The results were startling.

In 1984, a cohort of runners over age 50 were enrolled in a Stanford University study designed to follow wear-and-tear on the knees, through a series of X-rays.  At the time the study began, the research team expected to see more knee damage in the runners than in the control group.  However, when the study closed in 2002—after eighteen years of follow-ups—they found something unexpected> the runners did have slightly worse knees at the beginning of the study, but 18 years later, ratings of both groups were almost identical, indicating greater progression of arthritis in the knees of the non-runners. Furthermore, most of the runners were still running. In short, to quote the authors themselves, distance running was not associated with increased severity or progression of osteoarthritis of the knees in older adults. Similar results were reported in studies analyzing arthritis of the hip. Even more interesting, a study using measures to analyze cartilage compression following a recreational run found that cartilage is compressed while running—no surprise—but there were no biomechanical measures that correlated knee joint loading with stress across cartilage. Clearly, what running actually does to a knee and how that relates to injury is not as simple as was thought.

Could this mean that running might actually be good for knees? In truth, this is a difficult question to answer. Many other factors—genetics, weight, running mechanics, running surface, cross-training, and balance of muscle groups, among others—can influence the consequences of the aging process.  Studies like the ones described above attempt to control for these factors, but it is impossible to fully account for such confounding variables. Furthermore, there are other running-associated injuries not assessed by these studies—could there be an association over time between worsening patellofemoral syndrome and running, even if there is not an association with tibiofemoral arthritis? As more evidence continues to emerge, multiple lines of evidence seem to suggest that while running improperly can cause injuries and lead to ongoing problems, running well and uninjured might actually be protective. (Raising the question of how to avoid injury in the first place?

Addressing these questions will probably keep sports medicine physicians busy for decades. As our population continues to age and the health consequences of obesity become more prevalent, the benefits of regular, life-long cardiovascular exercise cannot be overstated. Running isn’t for everyone, but for those of us who love it, now we have one more reason to lace up those shoes and get going.