Anyone reading this that is a runner or a triathlete will have likely had quite a few people say to them over the years “I don’t run because it hurts my knees” or “What you are doing is bad for your joints” or “You are doing irreparable harm to your hips.” All of those statements are generally rubbish as most recent studies show that there is no link between degenerative conditions such as osteoarthritis and running. A part of the problem is the lack of quality studies in the past so be wary of older studies that do not stand up to modern scrutiny. If you want to look at some evidence yourself try going to Google Scholar, searching on “running osteoarthritis” and start reading. One recent (2015) summary of the available research concluded that “The weight of available evidence, albeit limited, suggests that recreational running is not a risk factor for knee osteoarthritis.” It does however observe a link between elite levels of running and osteoarthritis as well as confirming in the conclusions that there is currently not enough evidence to make a definitive statement. See ref 1 for more details.
The above can be summed up as recreational running is good for your joints, but at elite level running is too extreme and will likely cause long term harm. In other words everything in moderation, much like your burger and beer intake.
So what do I mean when I say that everything else is bad for your joints? Well, what running is great at doing is highlighting pre-existing problems such as muscle imbalances, or hidden RSI. If you look at how much of your life you have spent running and how much you have spent doing “other stuff” then you will see that running is a tiny part of your life. I run a lot for a recreational runner (very slowly and mostly offroad) and in 2015 I spent 360 hours running. That sounds like a lot, but it actually only comes to a total of 15 days. That leaves 350 days for “other stuff.”
Most of what you do the rest of the time is actually pretty bad for your joints. Let’s look at where I spent the rest of my time. Well I tend to get an average of 7 hours a sleep a night, so that takes care of another 106 days, leaving 244 days. I have an office based job, and probably spend the same again sitting. That is 106 days sitting a year, and if you count TV time it is probably more than that. If you add driving time onto that then it goes even higher. Wouldn’t running would have to be epically terrible for you if doing it for such a small percentage of the year could cause the harm that so many people think?
Instead let’s look at what sitting can do for you. Everyone says that sitting is bad for you, but they don’t often show how sitting can affect running. Ref 2 tells you why sitting is generally bad for you, but it doesn’t mention the joints. Essentially any degree of knee flexion (leg bending) places pressure on your knee, even if it is in an unloaded position such as while sitting or driving.
And don’t get me started on folk (mostly females) that wear high heels all of the time, particularly when growing up. Don’t do it girls. Save them for a night out, and wear flats as often as you can!
Ref 1: http://bjsm.bmj.com/content/early/2015/07/28/bjsports-2015-094749.extract
Ref 2: http://www.nhs.uk/Livewell/fitness/Pages/sitting-and-sedentary-behaviour-are-bad-for-your-health.aspx