Is Running Bad for Your Knees: The Science

“It’s great that you’re running but you know it’s bad for your knees right?” If runners worldwide had a dollar for every time they heard that we could band together and solve world hunger! In fact I might start collecting and become the voice of the movement. But is running bad for your knees what does the science say. These science posts usually come from something I want to know about too and this is no different. Sure I know a few facts I like to trot out about knee health but I don’t have a fulsome understanding of the subject. So let’s dig into the scientific literature and solve this problem.

This one could go either way. There sure is a lot of circumstantial evidence out there. My running aunt and uncle have matching knee scars though they still run. My yoga teacher has one too and she used to run too, that’s how she got into yoga. Hell, even my left knee acts up regularly enough. But we all know circumstantial evidence isn’t scientific evidence. Let’s go to the peer reviewed literature then!

Runner’s knee issues

There is not just one ailment that makes runner’s knees hurt but I do think non-runners are envisioning cartilage wearing down which is actually pretty rare. The most common knee injury is Runner’s knee (aka patellofemoral pain syndrome) which is not totally understood. The best evidence now is that the knee cap doesn’t track properly in the grove of the two bones of the leg. Another big one is Iliotibial (IT) band syndrome where the IT band which stretches from the hip to the knee ‘gets caught’ on the knob of the femur at the knee causing pain. The third big one is Patellar tendinitis where the tendon that connects the shin to the kneecap becomes inflamed. These injuries can be lumped together into a class called overuse injuries which do suck. But they are usually temporary and pretty quickly and easily healed with physiotherapy exercises.

There are of course other less common issues that can cause knee problems too. When people say running will ruin your knees they’re talking long term. In other words a condition that will lead to lots of long term pain, disability and potentially a knee replacement. That is symptomatic Osteoarthritis (OA). So we have two things to figure out here, does running cause knee injuries and does it in fact in the long term kill your knees?

Running and overuse injuries

It has been known for some time that the most common site of injury in runners is in fact the knee (Gent et al, 2006, Macintyre et al. 1991, Taunton et al., 2002). Score one for the peanut gallery there! Runners and athletes in general do get injured from time to time. Many studies have said that runners can expect an injury roughly every 1000 miles or so which can mean every year! The studies cited did all agree that runner’s knee is by far the most common complaint across genders, distances and ages of runners. So yeah runners can and should expect to deal with the odd knee injury. Interestingly studies also agreed that to a point running more each week (Gent et al., 2006) and the longer you’ve been running, especially past 8.5 years (Taunton et. Al., 2002) showed protective properties as well. Younger runners also experienced more knee injuries than their more aged counterparts (Taunton et al., 2002). This suggests that more experienced runners were less likely to have issues with their knees.

While it is dangerous to give circumstantial evidence too much credit these scientific studies do tend to back up what we see out on the streets (or the trails). There does tend to be a pattern as people get into running. That is they try it, love it obviously, then start running a 5k every other weekend. They keep pushing harder, faster and further and wind up injured. Unfortunately many give up entirely after an injury or two. But if you stick with it you learn more about best practices like the milage necessary to support a long run and only doing one speed session a week. The 10% rule is also a thing, hell you might even start incorporating strength training into your schedule. We learn what the first signs of injury are and act accordingly. We might even break out those physio exercises on the regular and manage our long term injuries effectively keeping us out of the doctor’s office in the first place. But there is no denying and the science doesn’t lie, yeah running, like a lot of other sports does cause knee injuries.

But does it ruin your knees?

In a word no. The studies and meta studies we’ve examined to this point are of people with knee injuries showing up at sports clinics or even just of runners showing up at clinics. Now it’s time to look at the other side of the coin and that is people with symptomatic (see disabling) knee issues. Were a higher than average proportion of those people runners? Again in a word no. It’s important to know that Osteoarthritis of the knee is the most common cause of disability over 60 years of age (Bosworth, 2009).

One study surveyed all osteoarthritis patients over 10 years. The were asked about their lifetime exercise habits up to that point. There was no increased risk of symptomatic osteoarthritis in patients that identified as runners at some point in their life (Lo et al., 2016). 

Weird right? Thousands of people with ruined knees studied and the runners in the group were no worse off or even represented at lower numbers? That can’t be right! Well let’s look deeper. Does physical activity ever pose a risk for one’s knees well the answer is actually yes. Physical activity is associated with an increased risk of knee osteoarthritis. However the level of activity required is pretty extreme. Patients who did more then 4 hours of heavy physical activity a day were at increased risk. Patients who did 3- 4 hours or less daily were not any more likely to develop OA (McAlindon et al., 1999). However if you are a person who does heavy physical labour or exercise for a living there is a warning here. You might want to talk to your doctor next time you’re in to ask what you can do to minimize damage to your knees over time.

But isn’t running for a long time all out obviously damaging? Nope! Lots of runners, crazy ones, race marathons. Meaning they are going all out for about 4 hours or so. In another study runners were given an MRI to look for knee damage before and after a marathon including regular runners and elites. Other than in one participant who had reconstructive knee surgery showed some slight damage after the marathon. No other runners did (Hohmann et al., 2004). If there is no detectable difference in the knees of runners before and after a marathon it’s pretty hard to make a case that even one extreme bout of running is damaging. So unless you are running for more than 4 hours on average daily then no running alone will not damage your knees in the long term.

Last argument then… Does running make OA worse? If you’ve got the first signs of arthritis in your knees you should stop running right? Again that’s a hard no. A meta study of patients with OA compared those that didn’t exercise compared to those that did and moderate exercise did not accelerate progression of the arthritis including running (Bosomworth 2009). So even if that niggle in your knee is the first signs of arthritis that’s not a reason to stop either.

Could running actually be good for your knees at 80?

Wait a minute might running actually protect your knees from OA? Well yes there is reason to believe that this is the case. One study followed the older members (above 50) of a running club for 18 years and compared their knees to those of control subjects who never ran.  Guess what the runners didn’t develop any more OA over the next two decades than those in the controls! In fact they had less and a higher BMI was the only lifestyle factor linked to developing arthritis (Chakravarty et al., 2008). In a similar study of running club members not only did the runners exhibit a rate of disability several times lower than the general public controls they also had a much lower mortality rate even when other lifestyle factors were controlled for (Fries et al., 1994). Not only do older runners have fewer knee problems, way less of them are disabled and fewer of them are dead! Now if that’s not an advertisement for running I don’t know what is! And as one final (giant) nail in the running is bad for your knees argument I present a meta study of over 125 000 participants which found that the incidence of knee OA in competitive (elite) runners was 13%, in recreational runners 3% and in control populations 10% (Alentorn-Geli et al., 2017). Now that’s a big finding with a really big n! So no, running does not ruin your knees as a recreational runner it actually protects them. That means that a recreational runner is more than three times less likely to develop OA than the person telling them that running will damage their knees. Even if your make your living running you’re only 3% more likely than someone in the general population to someday develop arthritis. That’s probably a fair trade off for all the very lucrative Instagram sponsored posts right?

Take away messages

Next time someone tells you that running is bad for your knees collect that dollar for our new worldwide hunger charity and challenge them. Does running cause short term overuse injuries well correlation isn’t causation but yes. Runners should expect an injury that takes them away from their sport for a few weeks every year or two. Plus you’ll have to do some stupid exercises to get back at it when it does. However as time goes on the longer you’re running the less often these sorts of issues will pop up. But long term damage no running does not in fact ruin your knees. Being physically active for more of your life actually protects your knees from damage. Science says so! The actual biggest risk factor for long term damage to your knees is a sedentary lifestyle and being obese. Both of which are the actual opposite of running!

So there you have it even though runners do suffer more overuse knee injuries just like all kinds of other activities running and being physically active is good for your knees in the very long term. Just out of curiosity how long have you been running and how many times do you estimate you’ve been told it’s bad for your knees? I’ll go first 22 years and 21 486 times! Leave yours (and any other thoughts) in the comments below!

Read what I read:

Alentorn-Geli et al., 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.

Bosomworth, 2009. Exercise and knee osteoarthritis: benefit or hazard? Canadian Family Physicians.

Chakravarty et al., 2008. Long Distance Running and Knee Osteoarthritis: A Prospective Study. American Journal of Preventative medicine.

Fries et al., 1994. Running and the Development of Disability with Age. Annals of Internal Medicine.

Gent et al., 2006. Incidence and determinants of lower extremity running injuries in long distance runners: a systematic review British Journal of Sports Medicine.

Hohmann et al., 2004. MR Imaging of the Hip and Knee before and after Marathon Running. Journal of American Sports Medicine.

Lo et al., 2016. Is There an Association Between a History of Running and Symptomatic Knee Osteoarthritis? A Cross-Sectional Study From the Osteoarthritis Initiative. Journal of Arthritis Care and Research.

Macintyre et al., 1991. Running injuries. Clinical journal of Sports Medicine.

McAlindon et al., 1999. Level of physical activity and the risk of radiographic and symptomatic knee osteoarthritis in the elderly: the Framingham Study. The American Journal of Medicine.

Taunton et al., 2002. A retrospective case-control analysis of 2002 running injuries. British Journal of Sports Medicine.