“I had to quit running because it’s bad for my knees” – Millions of people
If I had a dime for every time I’d heard that! I don’t actually know how much a dime is, being English and all. I’m guessing it’s something to do with “10”…10 cents maybe? I just Googled it, yep, 10 cents.
So I guess I wouldn’t have that much money, maybe a hundred dollars or something. But anyway. Since this is such common knowledge, it must be backed up by some pretty hard science right? Well, let’s find out!
I’m specifically interested in knee arthritis today. Everybody knows that you shouldn’t run because it causes knee arthritis. Also, everybody knows that if you have knee arthritis the first thing you should do is QUIT RUNNING. Now, all we want to do is figure out if this is actually correct.
What is Knee Arthritis?
We need to define terms a little first, but I always find defining terms the most boring part of writing an article! I did a quick Google search to see what the most popular definitions of knee arthritis were. I was surprised to learn that you can buy knee arthritis from Amazon and that you could receive it within 2 days with a Prime membership.
What a world we live in
I did find a better explanation in the following video. I think this shows the structural changes related to knee arthritis very well.
Before going any further, I’d also like to clarify that we’re talking about knee osteoarthritis. As opposed to rheumatoid arthritis. Rheumatoid arthritis is a systemic (body-wide) autoimmune (immune system attacks your own body) condition. It is something only diagnosed by medical professionals and far less common than run-of-the-mill osteoarthritis.
Osteoarthritis is often called “wear and tear”. Which is a horribly simplistic and unhelpful term in my opinion. One way I often explain this to clients is to imagine I took a photo of your face, I’d be able to guess roughly how old you are. Now, when we take an x-ray or MRI we are essentially taking a “photo” of your knee joint. In the same way, we should be able to tell roughly how old you are.
The wrinkles on my face and receding hairline are not “degenerative change”. Well, I suppose, technically they are! But they don’t hurt and I don’t worry about them. If my doctor took a photo of my face she wouldn’t say “Well, we can see signs of significant degeneration around the side of the eyes and the hairline”. But that’s exactly what we do with x-rays and MRI scans every day!
The fact is that we could also call these changes “normal, age-related change”. This issue is further complicated by the poor correlation between these changes and pain. You can have someone with “severe osteoarthritis” with no pain at all who can run 100km a week. You can have someone with no signs of arthritic change whose knee hurts when they walk for an hour. This is a very common story. Changes on imaging do not mean you will have pain. Osteoarthritic change in people over 40 with NO pain can be as common as 20-40% (Culvenor 2018).
For this reason the terms Symptomatic Osteoarthritis and Radiographic Osteoarthritis have emerged. Symptomatic Osteoarthritis refers to someone with “degenerative” changes on their x-ray or MRI AND pain. Radiographic Osteoarthritis refers to someone with “degenerative” changes on their x-ray or MRI but NO pain.
These changes are often graded as mild, moderate or severe on the imaging reports. These are usually referencing one of the classification systems such as the Kellgren-Lawrence classification for osteoarthritis.
Now, we don’t want to fall into the trap of thinking that x-ray or MRI findings are not important. Just because you can have grade 4 osteoarthritis in your knees and have no pain does not mean we want grade 4 changes in our knee. In fact, what we want to see is that as someone ages they have age-related change that is normal for their age.
If we take an x-ray of a 93 year old woman, we might be ok with seeing grade 4 changes in her knee. If we ask her, “does your knee bother you?” and she said “no, it doesn’t hurt at all” then we would call that radiographic osteoarthritis or normal age-related change.
However, if we take an x-ray of a 36-year-old woman and see the same grade 4 changes, we would be very concerned. Even if she said “my knee doesn’t hurt at all” we would still be interested because the changes in the knee joint are not in keeping with her age. This DOES NOT mean that this 36-year-old woman “will need a new knee within 10 years” (as pompous health professionals sometimes like to forecast). It is impossible to predict what will happen with this woman, there are far too many variables.
What it DOES mean is that we have some more information with which to discuss this woman’s plans. We take the x-ray results in the context of the woman in front of us. We discuss the pros and cons of different lifestyle habits, diets, career choices and recreational activities. Then we make a plan, execute that plan and review how it is going at an appropriate interval (yearly might be good in this case).
If this woman is a runner, then we need to talk about whether continuing to run is a good idea. In order to do that with some connection to reality, we need to look at the research to see how running affects knee arthritis. Does it make it worse? Does it make it better? How much is too much? Was this caused by running in the first place?
Well, let’s look at some of the research…
Does Running cause Knee Arthritis?
From 1984 to 2002 Chakravarty and colleagues followed 45 long-distance runners and 53 non-runners. They had “originally hypothesized that long-distance running may be associated with increased incidence and severity of OA”. However, when reviewing the x-rays almost 20 years later they were surprised to find that “long-distance running was not associated with accelerated incidence or severity of radiographic OA” (Chakravarty 2008).
In 2016 Timmins and colleagues did a big meta-analysis of all the research on running and knee osteoarthritis. Unfortunately, they found mixed results. They concluded that “moderate- to low-quality evidence suggests no association with OA diagnosis” (Timmins 2016). Interestingly, their results suggested that running may offer some protection against needing a knee replacement later in life.
In 2017 some researchers from Spain performed a systematic review and meta-analysis of all of the research on hip and knee arthritis and its relationship to running. Of the subjects analyzed, roughly 10% of the non-runners had knee or hip arthritis whereas only 3.5% of the recreational runners did.
However, they did find that roughly 13% of the “competitive” runners had hip or knee arthritis. They defined “competitive” runners as “professional, elite, or ex-elite athletes” (Alentorn-Geli 2017).
After analyzing 25 trials they concluded:
Recreational runners had a lower occurrence of OA compared with competitive runners and controls.
Alentorn-Geli 2017
"recreational running" may be beneficial for hip and knee OA but "competitive running" may be as bad as being "sedentary"
The higher prevalence of knee arthritis in “competitive” runners in Alentorn-Geli’s study are in line with the findings of Kujala in 1995. Kujala and colleagues compared the knees of former professional runners with former professional soccer players, weightlifters and shooters. Knee arthritis was found in 14% of the runners (compared with 3% in shooters, 29% in soccer players, and 31% in weight lifters) (Kujala 1995). So it may be that “recreational running” is protective against knee arthritis, but “competitive” running is not.
The take away from this study may be that recreational runners don’t seem to suffer from hip or knee arthritis worse than non-runners. So does running cause knee arthritis? Probably not. However, “competitive” runners may be a different story, we need more research to determine if there is such a thing as “too much” running.
But what about runners who already have knee arthritis? Won’t they make it worse if they keep running on it?
Does Running Make Knee Arthritis Worse?
That’s what Dr. Lo and her colleagues at Baylor College of Medicine set out to investigate. They published a paper in which they asked 1200 people with knee arthritis to answer some questions to help them identify the runners in the group. When they compared the runners to non-runners they found that the runners actually appeared to have less knee pain and it was less likely to get worse over the 8-year study period. They also took x-rays at the beginning and end of the trial and found that the structural signs of knee arthritis had not worsened in the runners (Lo 2017).
Our study provides the first evidence to guide recommendations regarding whether people who have knee OA should be advised to run or not … our study is reassuring because among those who had knee OA who choose to run, running did not appear to be harmful. In fact, there was a beneficial effect of decreased pain symptoms in runners with knee osteoarthritis.
Lo 2017
Some good evidence that self-selected running is not harmful for knee OA
A recent small study looked a little closer at the changes in cartilage (joint lining) in response to running. They took 10 female runners who had symptomatic knee arthritis and did an MRI scan on them before and after running. They were looking for differences in how the cartilage responds to the load. Specifically the water-content of the cartilage. Essentially, running squishes out some of the water from the cartilage. In “normal knees” the cartilage recovers this water quickly. However, in “arthritic knees” it seems to take a little longer to recover (Esculier 2019).
This may provide some evidence that runners who know they have knee arthritis should leave bigger gaps between each run. Perhaps avoiding running every day.
Honestly, that is a bit of a leap based on one small study that wasn’t specifically looking at this question. This is more just food for thought.
Runners with knee arthritis may need longer between runs to allow their cartilage to recover
It looks like the jury is out on that one. Reviewing the current evidence it would seem that recreational running is neither likely to give you knee arthritis, or make it worse if you already have it. Actually, the evidence would seem to suggest that your knees will be healthier than those of your more sedentary counterparts.
However, it may be that those runners who already have knee arthritis need to be a little more careful than non-runners. It may also be that more competitive runners will lose out on the “protective effects” that recreational runners seem to enjoy. This is the part where the jury is still out. There is not much research to say how much running is “too much” or even to say that running volume is the problem. Hopefully, we will have more research to parse this out in the future.
For now, it is pretty safe to say that your knees will not be worse off if you’re a runner, competitive or recreational.
My Advice
If you don’t have knee arthritis, please don’t worry about it, just run. The health benefits accrued by running far outweigh the risks of knee arthritis. Even if you run tons there doesn’t seem to be any evidence that you’re worse off than a sedentary person.
If you do have knee arthritis. Listen to your knee. If you are running a certain amount each week and your knee seems to be tolerating it (not getting more painful each week), then keep going. If it’s getting more painful, or you can’t run as much as you want, go and talk to a Physiotherapist with an interest in running. There are lots of things you can do to help with knee arthritis. Strength training for runners is a good place to start.
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