i ride my bikes, mostly my fixie, like 90 miles to and fro work every week up some big hills (and down, BRAKELESS) and my knees have been killing me since i started riding my fixie more and more. hell, theyre killing me right now and i havent been on a bike in like 20 hours. i can ride 60 miles on a road bike and not have knee pain the next day. i have a theory that in like 20 years all the hipsters and people who have suddenly started riding fixies (yeah, im one of em too) will be a generation with mass knee problems. every used-to-be-hipster when theyre 50 (in like 2035) will be writing on knee replacement forums. but by then i hope kickass knee surgery is readily available and cheap. today the medical market caters to baby boomers, but in a few decades itll be all about old timer hipster joint surgery. the comercials for hospitals would be so funny, thered be like a burnt out hipster and he'd be like "hi, im so and so i and i used to drink pbr every day and smoke lots of cigs, but i also rode a fixie. i had the whole campy setup on my 1978 schwinn, i even had a reload bag! but by 2012 my knees were ****ed up and i couldnt walk- that was, until i found the kind people at said hospital who replaced my knees. replace now and theyll even throw in free tatoo removal". ive started to save my pocket change for a new bmw fork for barspins AND the rest for knee replacement surgery. ive scheduled it with my friend who plans to go to med school , that he'll surgerize me when it comes time.