It has been a long standing myth amongst non-runners that running (specially long distance running e.g. marathons) can cause arthritis and damage the knees. Infact one of my friends who is an ergonomist and occupational therapist also said the same thing to me. She is an ardent cyclist and swears that pounding the knees on the roads is not her idea of exercise as its going to have a significant impact on her knees and leave her with early onset of osteoarthritis in the knee. She has even encouraged me to consider giving up running and take up cycling as an exercise instead as it is potentially less strenuous for the knees.


One can be forgiven for believing these contentions. It is easy to imagine ballistic forces moving through our knees when running and since the knees of long distance runners undergo these mechanical forces repetitively, it can be assumed that it would lead to degeneration and therefore knee osteoarthritis.

But is this really the case? Does running cause knee osteoarthritis or even contribute to its earlier development. Let’s see if there is any evidence for this assertion.

Timmins et al (2017) undertook a systematic review and meta-analysis to explore this issue. Based on 25 articles and 15 studies, the authors found conflicting evidence for the association of running and knee osteoarthritis, but authors reported 50% reduced odds of surgery due to knee OA in runners. 

Chakravarty et al (2008) evaluated the differences in the progression of knee OA in middle- to older-aged long distance runners (45) when compared with healthy nonrunners (53) over nearly 2 decades of serial radiographic observation. The authors reported that regression models found higher initial BMI, initial radiographic damage, and greater time from initial radiograph to be associated with worse radiographic OA at the final assessment; no significant associations were seen with gender, education, previous knee injury, or mean exercise time. The authors concluded that long-distance running among healthy older individuals was not associated with accelerated radiographic OA. 

In a retrospective study of 2,637 participants, Lo et al (2017) utilised knee radiograph readings, symptom assessments, and completed lifetime physical activity surveys to evaluate the relationship of running with knee pain, radiographic osteoarthritis (OA), and symptomatic OA. They found that no increased risk of symptomatic knee OA among self-selected runners compared with nonrunners in a cohort recruited from the community. In those without OA, running does not appear to be detrimental to the knees. 

More recently, Ponzio et al (2018) evaluated prevalence of pain, arthritis, and arthroplasty, and associated risk factors in active marathon runners. A hip and knee health survey was distributed internationally to marathon runners. Active marathoners who completed ≥5 marathons and were currently running a minimum of 10 miles per week were included (n = 675). Questions assessed pain, personal and family history of arthritis, surgical history, running volume, personal record time, and current running status. Age, family history, and surgical history independently predicted an increased risk for hip and knee arthritis in active marathoners, although there was no correlation with running history. Additionally, the authors reported that the arthritis rate of active marathoners was below that of the general U.S. population. 

Though unrelated to knee, with nearly 90,000 participants, the National Runners’ and Walkers’ Health Studies were the largest prospective cohorts specifically recruited for the study of health benefits and risk of physical activity. Participants reported whether a physician had told them they had osteoarthritis and if they had a hip replacement since their baseline questionnaire and reported the year of diagnosis or replacement. The authors reported no evidence than running increases the risk of OA, including participation in marathon races, and, in fact, subjects that ran ≥1.8 METhr/d (≥12.4 km/wk) were at significantly lower risk for both OA and hip replacement. Their data even showed that neither marathon frequency, marathon intensity, nor 10-km intensity predicted any increase risk for OA or hip replacement (Williams 2014). However, it must be stressed that the findings were based on self-reported OA as compared to radiographically diagnosed OA. 

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There are of course some studies which have shown increased prevalence of osteoarthritis in runners. A recent systematic review by Driban et al (2017) reported that participants in soccer (elite and nonelite), elite-level long-distance running, competitive weight lifting, and wrestling had an increased prevalence of knee OA. However, in this review, there was no significant comment made in relation to recreational long distance running.

So from the evidence available, it appears that running MAY NOT be associated with increased prevalence of osteoarthritis. However, it must be remembered that the quality of evidence is low to moderate at best and there is lack of high quality longitudinal data.

This is in contrast to other individuals with physically demanding occupations such as miners, farmers, and jackhammer operators who have a greater risk of OA than the general population and athletes in other weight-bearing sports (e.g., soccer, weight lifting) have a greater risk of OA than runners even after controlling for traumatic knee injury (Miller 2017).

But then does it defy common notions? How is it possible that despite greater loads being transferred to knees during running, there is no association with greater arthritis?

Vincent et al (2012) in their review of the pathophysiology of knee osteoarthritis highlight that the initiation and progression of knee OA involves mechanical, structural, genetic, and environmental factors. They stated that during growth and development, the tibial and femoral cartilage adapt over time to cyclic loading. Because knee cartilage thickens in the areas of greatest loading in both the anterior-to-posterior and medial-to-lateral regions, the tibiofemoral mechanics and loading patterns during load bearing have a significant influence on the regional development of articular cartilage. Normal healthy cartilage responds positively to loading and increases regional thickness. From this we may be able to conclude that running may have a positive impact on cartilage health.

Miller et al (2014) compared the peak load and per unit distance (PUD) load between human walking and running in 14 healthy adults. Ground reaction force and motion capture data were measured and combined with inverse dynamics and musculoskeletal modeling to estimate the peak knee joint loads, PUD knee joint loads, and the impulse of the knee joint contact force for each gait with a matched-pair (within-subject) design. Compared with walking, the relatively short duration of ground contact and relatively long length of strides in running seem to blunt the effect of high peak joint loads, such that the PUD loads are no higher than that in walking. 

Miller (2017) propose two mechanisms as the explanation for why this may be the case. The first one is that cumulative load and peak joint stress in running may not be particularly high and secondly joint loads in running condition cartilage to withstand these stresses without joint deterioration. These theories need further evaluation. 

Conclusion

Whilst it may appear that due to increased joint loading, running may be associated with increased prevalence of knee osteoarthritis but from the literature, it appears that running MAY NOT be associated with increased prevalence of osteoarthritis. However, it must be remembered that the quality of evidence is low to moderate at best and there is lack of high quality longitudinal data. 

But would you wait for further high quality evidence to decide either way or like me, consider the health benefits of running and just get on with it? What do you think? 

Clinical, MSK, Research, Sports

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