For many years medical dogma and anecdotal evidence has suggested running is bad for your knees and causes arthritis. Many well meaning health professionals have advised runners to cut down or even stop running altogether to protect their joints, but the evidence remains weak to guide their management. Richard Leech's excellent BJSM editorial discusses this in more detail and he joins us today to share his considerable knowledge on the topic.
Follow Richard and his research on Twitter via @TheHALOstudy.
Osteoarthritis (OA) is the subject of much research and interest from athletes and patients. The effect of running – one of the most popular sporting activities in the UK – on overall joint health and the risk of developing (or worsening) OA remains unclear.
Anecdotally, many individuals consider running detrimental to their knees and either do not run at all in fear of causing themselves harm, or proceed to participate in alternative sports, such as cycling. The evidence to date is limited, particularly in relation to advising runners with a diagnosis of joint pain and/or OA.
Running and Load
OA has been described as a mechanically driven condition; its development requires increased or altered loads to be imposed upon a susceptible joint (1). How much, and in what way, these loads (e.g. during running) are applied is critical.
OA occurs when the ‘dynamic equilibrium’ of a joint (2) – describing the balance between stresses and repair processes – cannot be maintained.
The underlying joint health (particularly of the cartilage) dictates the response to load. Evidence suggests that the components of joints do not respond uniformly to running, and there are high individual differences (3).
Studies have shown immediate knee cartilage deformation following running, the extent of which appears to increase with distance (4,5,6), yet joints exhibit highly efficient repair processes. Consequently, healthy joints of well-trained individuals do not seem to be adversely affected as a result of marathon running (in the short (7,8) or long term (9)).
Long-term adaptations, such as increases in joint surface area, have been identified amongst trained endurance athletes (10). Another study infers completion of a 10-week ‘Start to Run’ program could help protect the joints of novice runners (11). Such changes may be beneficial, ensuring the knees are capable of withstanding the loads imposed by running (Figure 1), but their ultimate relation to overall risk of OA remains unknown.
Running and OA Progression
As with any structure, excessive, repetitive loading will eventually lead to failure. It would therefore seem logical to consider long-term participation or high-intensity running as detrimental to the knees. Every mile, 1,000-1,500 ground impacts occur equating to 2800 tons acting upon the hip, knee and ankle in a 70kg runner completing a marathon (8).
Changing the amount or type of running (in the short or long-term), or running whilst fatigued (e.g. completing endurance events with inadequate preparation or insufficient rest between activities), could inhibit normal muscle function. This ‘muscle dysfunction’ (12) reduces their contribution to force absorption around a joint, thus exposing it to potential damage.
A subsequent imbalance in maintaining joint health – where damage exceeds repair – initiates a cascade that may result in osteoarthritic changes and ultimately joint failure (Figure 2). The rate of progression is related to the degree of further loading (13). Theoretically at least, running could have a role increasing the rate of OA progression.
The cumulative effect of running does not appear to lead to joint ‘wear and tear’. If this were true, all runners would get OA but this is not the case. Few studies have explored the effect of running on OA progression. One group has reviewed runners and controls at 2, 5 and 9-year follow-up (14-16), with no significant differences observed.
In another study, x-rays of runners and non-runners were compared. At baseline the two groups presented differently – runners tended to have worse findings, but at follow-up (mean 11.7 years), there was no difference (17). Controls therefore tended to have a greater rate of progression compared with runners, but again the result was not significant.
Another smaller study concurred with the findings above (18). No differences between the joints of runners and non-runners were found following an 8-year study period.
Running, Function and Pain
Studies have shown that runners benefit from lower age-related pain and disability compared to sedentary controls. Throughout a 14-year study, pain increased with ageing amongst all participants (regardless of running status) but the initial favourable pain scores amongst runners persisted and remained lower by approximately 25% throughout (19).
Similarly, running was associated with higher function as ageing occurred (20). A further study found the greatest benefit amongst female runners and those who were members of running clubs. There was no difference between the volume of running (mins/week) and disability severity, which may indicate no adverse physical effect of higher intensity running (21).
High-level competition has also been explored. Analysing retired, elite (Olympic / international) athletes, long distance runners reported more favourable outcomes compared with athletes from other sports. In fact, the runners had the lowest risk of knee disability of all athlete categories (22).
It is important to remember:
- Many studies include small sample populations; these are often older athletes that have been able to remain active in later life and may not accurately represent the wider running community
- There is a poor correlation between x-ray findings and reported symptoms (joint pain)
- The effects of running at different times in life (and at varying amounts) have not been specified
- Identification of OA progression, rather than incidence, is methodologically and clinically challenging. The condition is a continuum, and implementing arbitrary thresholds to measure change is innately limited (23)
The true effect of running remains unclear – regarding the onset or progression of joint pain and OA. The wider health benefits of running should be reinforced and an active lifestyle encouraged. Replacing outcomes relating to imaging (e.g. x-rays) with subjective reports of symptoms and disability highlight the general musculoskeletal benefits of running.
If they exist, loading tolerance thresholds (i.e. the amount of running before risk of OA increases) are likely to vary between individuals. In the absence of strong evidence, it is perhaps sensible to suggest exercise should be enjoyed symptom free, with no subsequent adverse reaction.
Finally, athletes/clinicians should acknowledge a) the potential risks of running, b) the conceivable long-term consequences of severe joint injury and c) the importance of appropriate conditioning and injury prevention strategies.
It's important to remember every individual's situation is different. If you have any concerns about arthritis or your joint health please see a physiotherapist or health professional for advice and treatment specific to your needs. As we often say on Running Physio if in doubt get checked out!
Richard is a PhD student with the Arthritis Research UK Centre for Sport, Exercise and Osteoarthritis at the University of Nottingham. He is exploring running and the impact it has on knee pain and joint health.
Details of ongoing research at the Centre can be found at:
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