You're correct that obesity has a negative effect on people's knees (OA, degeneration, etc.) I'm not disputing that.
The question though, is whether the activity of running causes or accelerates knee problems. I've provided a study that suggests it doesn't. If you find a study which suggests that running does cause problems, or a study which involves obese runners (or people who were obese, then lost weight) then I'm happy to look at that.
Honestly though, I doubt you'll find a study with obese runners. For obvious reasons, obese (even overweight) people have numerous other physical limitations that would prevent them from running any reasonable distance. Thus, how could you conduct a long-term study with obese patients who run regularly? Not going to happen.[q]
http://www.jrheum.com/subscribers/04/04supp/2.html
also, it's one of those "what came first, chicken or egg" kinds of things with the knee oa and obese people running. just doing a brief google search to see what i could find out there, i see lots of statistics about obesity being linked to knee oa, but nothing about obese people running long distances being linked to oa. i would image that it wouldn't matter... obesity being linked to oa is obesity being linked to oa, running or not.
[q]I understand your thinking here. Current medical research suggests that I can prevent future problems by having regular dental checkups, eye exams, etc. so I do those. I'll get regular prostate exams once I turn 40, and I would get mammograms if I were female.
But as this thread demonstrates, the research on running and knee issues is mixed at best. There isn't a recommendation to get regular knee x-rays if you run regularly and from my own research I don't see a need to, so I don't.[/q]
that's because, to the average person, it's a waste of medical dollars. however, to an elite athlete, it's preventive and precautionary. everyone has teeth, so they say "get your teeth checked"... every male has a prostate, so they say "get your prostate checked"... every female has breasts, so they say "get your mammogram". they don't say "if you're a runner, make sure you get your knees, feet, and low back checked"... it's just not that big an issue and such a small percentage of the population is actually active enough to worry about it. they don't tell obese people to get things checked because what's the point? it's just a natural progression of their obesity to have bad knees... why bother?
this country wastes so much money on sick care that they don't even worry about people's health care. health care should be just that... caring about peoples' health and making sure they don't get sick... preventive measures and patient education is what it should be all about... not "i only go to the doctor when something's wrong". it's a silly way of looking at it. the government doesn't care for what keeps people healthy. if someone didn't know there was a looming problem that would cause major problems down the road if they didn't start treatment right away, why would they take any action at all? that's how money is made, i suppose... letting people unknowingly destroy themselves to the point where they need to spend lots of money and time to try and fix it when they could have spent less time and money overall if they dealt with it earlier on...
but i digress...
[q]Yes, runner's knee is more common in runners. But keep in mind that many runners don't do the recommended strengthening exercises which can prevent runner's knee or alleviate symptoms. I'd guess that's why patellofemoral pain syndrome is so common, and why it's been given the name "runner's knee".
This is in contrast to general knee degeneration, which it is hypothesized can occur from accumulated running, regardless of preventative strengthening exercises.