I was playing for a couple months at home before my psoriatic arthritis kicked in on my right foot...but I'm getting much better after a few rounds of injections. I had figured that it would be good for me knees, but I guess if you overdo it then it isn't. Is there any scientific or anecdotal evidence that, in general, DDR is bad for your knees? Or is it just that people keep getting into heavier and heavier routines as they get more experience?