A common thing us physios hear, either in the clinic or out at a social event, is the statement of “running is bad for your knees” or “running causes arthritis”. Lots of people believe this to be true, most of the time because they’ve heard it off someone else, and so the idea of today’s blog is to see if we can shed some light on the issue.
When we look at the body of evidence, much of the limited research that’s been undertaken on the issue has used either poor quality designs, small sample sizes (numbers of people in the study), or both. Although this is the case, it doesn’t mean that the evidence should be discarded, just that we should take caution when interpreting the current research base. What we can derive from the current evidence base is that not only is there a lack of a clear link between running and osteoarthritis, but some more recent evidence may even point to a protective effect of running on knee joint health.
What is Osteoarthritis (OA)?
OA is often described as ‘wear and tear’ of the knee. Although this may be true in some regards, it is much more complex than that simple notion. The latest evidence points towards an abnormal balance between the cellular processes that build and repair tissue, those that break down tissue, and systemic inflammatory processes. The body is constantly adapting via these processes, usually in a positive way, to make us stronger and more robust. Although, if the breaking down is happening at a quicker rate than the repairing processes, then we may be negatively adapting those structures and weakening them as a result. In the knee, this imbalance can result in cartilage and soft tissue breakdown, which can eventually lead to joint deformation if it occurs over a long enough period of time. Importantly, structure is only a part of the bigger picture, as we know that X-rays findings have little correlation with the amount of pain or disability a person is experiencing (i.e. a person can have no symptoms but significant joint changes, or conversely we can see a person with high levels of pain and disability who has relatively small joint changes). For this reason, we see X-rays as only part of the bigger picture.
So does running cause OA?
There is no strong evidence that points towards an increased level of knee OA when comparing runners to sedentary people. In fact, there is some evidence that shows that recreational runners (non professional/elite competitors) actually have thicker cartilage and lower rates of knee OA than sedentary individuals or non runners. The rates of OA are higher in those elite runners (who average >100 km’s per week) than the recreational runners, although the data shows that even the elite runners have lower rates of OA than the sedentary individual. This seems to fall into line with the balance of cellular processes that we talked about earlier. Some running, when done in a graded manner which allows for repair of the cartilage in the knee, is actually beneficial to knee health. Whereas underloading (sedentary individuals), or drastically overloading (elite runners) may cause an imbalance of the aforementioned cellular processes that could result in joint damage. Recent evidence also supports this thinking, showing a protective effect of a graded running program when implemented by sedentary individuals who trained for a half marathon.
So are there any risk factors linked to developing OA?
Yes! A recent study focusing on marathon runners showed that age, family history of OA and surgical history in the knee or hip were independently associated with rates of OA. This doesn’t mean that if you have a family history, are older, or have had joint surgery that you are destined to has symptomatic OA, but more so highlights that if you do have any of these risk factors, that you should ensure that you have a personalised running program if starting up or starting to train for something like a marathon.
It seems as with most musculoskeletal issues, movement is key however we need to be smart by starting slowly and establishing a thorough training plan when starting new activities. The Goldilocks principle applies – not too much, not too little is just about right!
References
Alentorn-Geli, E., Samuelsson, K., Musahl, V., Green, C. L., Bhandari, M., & Karlsson, J. (2017). The association of recreational and competitive running with hip and knee osteoarthritis: a systematic review and meta-analysis. journal of orthopaedic & sports physical therapy, 47(6), 373-390.
Miller, R. H. (2017). Joint loading in runners does not initiate knee osteoarthritis. Exercise and sport sciences reviews, 45(2), 87-95.
Ponzio, D. Y., Syed, U. A. M., Purcell, K., Cooper, A. M., Maltenfort, M., Shaner, J., & Chen, A. F. (2018). Low prevalence of hip and knee arthritis in active marathon runners. JBJS, 100(2), 131-137.
Van Ginckel, A., Baelde, N., Almqvist, K. F., Roosen, P., McNair, P., & Witvrouw, E. (2010). Functional adaptation of knee cartilage in asymptomatic female novice runners compared to sedentary controls. A longitudinal analysis using delayed Gadolinium Enhanced Magnetic Resonance Imaging of Cartilage (dGEMRIC). Osteoarthritis and cartilage, 18(12), 1564-1569.
