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Running is often perceived as bad for your knees.1 In particular, concern exists regarding the development and progression of knee osteoarthritis due to long-term exposure to running.1
Despite these fears, recreational running does not have negative consequences on knee joint articular cartilage in runners without symptomatic knee osteoarthritis2 3 and may actually be beneficial for long-term joint health4 (see figure 1). Only 3.5% (95% CI 3.4% to 3.6%) of recreational (amateur) runners have osteoarthritis (knee or hip) compared with 10.2% (95% CI 9.9% to 10.6%) of sedentary individuals.4 However, a dose–response relationship may be present; 13.3% (95% CI 11.6% to 15.2%) of elite or ex-elite runners (competitive professional athletes of an international level) had osteoarthritis, a higher rate than seen in recreational runners.4 While knee cartilage may undergo acute changes during a run (eg, reduction in cartilage volume and thickness, oligomeric matrix protein increase), these changes are likely to be temporary in runners without knee osteoarthritis.2 3 5 Evidence relating to the influence of repeated exposure to running on cartilage morphology and composition remains limited.5
Infographic
What if a runner already has knee osteoarthritis?
Fear of causing pain or further osteoarthritis progression likely leads many runners to reduce or cease running following a diagnosis of knee osteoarthritis.1 To date, little evidence exists to guide such decisions. A single study reported that running does not appear to accelerate the progression of knee osteoarthritis in runners aged ≥50 years, and runners with knee osteoarthritis reported more improvement in knee pain compared with non-runners with osteoarthritis over a 4-year period.6 These findings support earlier prospective research which reported that long-distance running among healthy older individuals was not associated with accelerated radiographic knee osteoarthritis.7 A small study (n=20) of runners suggested that knee cartilage in runners with knee osteoarthritis does not recover as quickly after a 30 min run as the cartilage in runners without knee osteoarthritis.8 These findings suggest that runners with symptomatic knee osteoarthritis may benefit from running less frequently to allow for sufficient cartilage recovery time between running bouts. Overall, more research is needed to provide definitive guidelines for runners with knee osteoarthritis on the optimal run frequency, intensity and volume.
So, what should clinicians tell runners?
Further high-quality prospective research is needed to improve our ability to educate runners about the risks or benefits of running to osteoarthritis development. However, current evidence suggests that running may have a protective effect against the development of knee osteoarthritis, provided sustained elite-level training is avoided.4 However, ideal running training load (ie, intensity, volume, frequency) to optimise knee joint health for runners with and without knee osteoarthritis remains unclear.3 4 Other factors, such as older age, excessive body mass, heavy occupational workload and previous traumatic knee injury may be more relevant risk factors for knee osteoarthritis than running alone.4 However the confounding influence of these risk factors in runners is yet to be determined.4 Runners with knee osteoarthritis should feel safe continuing to run, since running does not appear to accelerate the progression of existing knee osteoarthritis.6 Given the overwhelming health benefits associated with running, it is currently not sound advice to tell a runner with knee osteoarthritis who is managing their symptoms to cease or reduce running participation.
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Acknowledgments
The authors would like to acknowledge the contribution of Katherine Parker in assisting with the infographic design.
Footnotes
Twitter @JamesA_15, @rwilly2003, @agculvenor, @DrChrisBarton
Contributors JLNA and CJB conceived the idea. JLNA led development of the infographic and accompanying text. All authors contributed and approved the final infographic and accompanying text.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests CJB is a deputy editor and AGC is an associate editor of BJSM.
Provenance and peer review Not commissioned; externally peer reviewed.