For the longest time, we have been told that we should fear high-impact activities, such as running, but our understanding of knee OA has evolved significantly over the years...
Written by Anthony Teoli, MSc, PT
This blog article was inspired by a conference podium presentation I had attended on osteoarthritis (OA) management. This presentation was being given by an experienced physiotherapist, to a rather large audience of patients and healthcare professionals. The speaker described knee OA as a degenerative disease characteristic of “wear-and-tear”. When speaking of the importance of exercise in the management of knee OA, the speaker stated that running and other high-impact exercises and activities were not appropriate and were to be avoided at all costs. These activities were said to be “dangerous” because of their potential to “create more damage” at the knee and consequently, worsen their condition. Afterward, the speaker advised that all exercise in patients with knee osteoarthritis were to be pain-free, as this was key to not “creating more damage” or “making their knee OA worse”.
Does running cause knee osteoarthritis?
For the longest time, we have been told that we should fear high-impact activities, such as running. We have been told that running damages the knees and leads to OA. Our understanding of knee OA has evolved significantly over the years. We now know that knee OA is more than just a consequence of aging (i.e. “wear-and-tear”). It is a complex and multi-factorial condition that affects the entire joint, and not just the articular cartilage. We also know that the experience of pain does not necessarily equate to tissue damage, especially in a chronic condition such as knee OA. Therefore, the pain that the patient is experiencing may be an indication that the knee is more “sensitized”, and should be used to help guide exercise selection and dosage, but not to limit them. We also need no longer vilify running. Current evidence would suggest that not only do recreational runners not have an increased risk of developing knee OA, but running may even have a protective effect! Let’s review some of the evidence:
Chakravarty et al., 2008
This prospective study examined 45 long-distance runners and 53 controls with a mean age of 58 (range 50–72) years from 1984 to 2002 with knee radiographs. In 1984, the prevalence of knee OA in long-distance runners was 6.7% in runners compared to 0% in controls. In, 2002 the prevalence of knee OA in long-distance runners was 20% in runners, compared to 32% in controls. According to their regression models, higher initial BMI, initial radiographic damage, and greater time from initial radiograph were found to be associated with worse radiographic OA at the final assessment. In addition, by the end of the study, runners did not have more prevalent OA nor more cases of severe OA than did controls.
Alentorn-Geli et al., 2017
This systematic review and meta-analysis examined 22 studies with over 100 000 pooled participants. The prevalence of hip and knee OA was 10% in controls/non-runners, 3.5% in recreational runners, and 13% in elite runners. It is important to note that elite/competitive runners were runners who were professional, elite, or ex-elite athletes, or in any case in which runners represented their countries in international competitions. These individuals are a small sub-set of the running population and are not representative of most runners. What is most important to retain from this study is that knee OA is three times less likely in recreational runners (who are representative of a good portion of the running population) when compared to sedentary, non-runners. However, appropriate dosage of running may be an important factor, given high-level competitive runners are more likely to have knee OA than recreational runners.
Timmins et al., 2017
This systematic review and meta-analysis of 15 studies aimed to determine the association between running and the development of knee OA. Their results demonstrated that running may have a protective effect, reducing the chances of surgery due to knee OA by 54%!
Rhim et al., 2019
The purpose of this article was to evaluate any degenerative changes in the knees and spines of six recreational runners (ages ranging from 56 to 70 years old) who completed at least 1000 marathons. Magnetic resonance imaging (MRI) of both knees and spines of the six runners was performed with a 1.5 T MR scanner. The anatomical structures of the knee joint including meniscus, bone marrow, cartilage, ligaments, and joint effusion were examined, along with other abnormalities. Spinal alignment, degenerative change in intervertebral disc, intervertebral disc herniation, osteoarthritis in facet joint, degenerative anterior/lateral spur, and other abnormalities were evaluated.
The results of this study were the following : one runner showed degeneration at the meniscus, while three runners had cartilage lesions. However, none of the six runners showed radiologic evidence of knee OA. All six runners demonstrated degenerative changes in intervertebral spinal discs. Due to the design of this study, it is impossible to attribute the degernative changes in the spine found on MRI to running, as other important factors such as aging could also explain these findings, especially given approximately 80-93% of asymptomatic individuals between the ages of 50 and 70 years demonstrate degnerative spine changes (Brinjikji et al., 2015).
Although the sample size of this study was limited (n=6 participants), their results would challenge the common belief that knee OA is caused by “wear-and-tear” of the knee joint. You might initially be tempted to think that more active individuals (i.e. individuals with a greater number of loading cycles) would have a higher incidence of knee OA when compared to their less active counterparts. This is simply not the case!
Generally speaking, our patients should not be discouraged from running. First and foremost, running is beneficial for overall health. Second, running has a positive effect on the knee joint when the appropriate load is applied. These benefits include but are not limited to, increased bone mineral density, increased capacity of the muscles, decreased inflammation of the knee joint and stronger cartilage. Third, recreational runners do not appear to have an increased risk of developing knee OA and running may even have a protective effect.
However, there may be special considerations that need to be made for recreational runners with knee OA. For instance, recreational runners with knee OA may require more time for recovery following a run. Ideally, running should not worsen morning stiffness and swelling, or significantly increase pain for a prolonged period of time following a run. As a result, runners with knee OA may also wish to consider adjusting training according to symptoms (ex : running shorter distances or running a bit slower). If this is still not sufficient, then the patient can try other less symptom-provoking activities to increase load tolerance, prior to attempting to run again. It is important to emphasize that these recommendations are mainly on expert consensus, as limited empirical evidence is available to inform clinical recommendations.
I would like to conclude by acknowledging that we are far from having all the answers. Research examining the effects of running as an intervention in patients with knee OA is very limited. Promoting running in those with pre-existing knee OA who have never run before may have unknown consequences. Running appears to have a protective effect on knee osteoarthritis but we cannot say for sure how a non-runner with pre-existing knee OA would respond in the short or long term. Is there a sub-set of patients with knee OA who would respond well or poorly to running? Can and should patients with unicompartmental or total knee arthroplasties run? Would it be ill-advised? We simply do not know, at least for the time being. What we do know, however, is that recreational running does not increase the risk of developing knee OA and should not be discouraged or vilified as a mode of exercise simply because it is considered to be “high-impact”.
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