it'll be hit or miss whether these bother the back of your knees. Specifically, it's the velcro on the flap that is the culprit. I have removed the velcro from the outside of the flaps (not on the strap) and this problem went away. the velcro also reinforces the flap so it is a bit stiff, but by removing it, the flap just forms to your legs. It feels like it breathes better and I won't need to worry about pedaling with these on. It's a really nice knee / shin guard but the straps is poorly designed. It's wider than it needs to be. If they reduce the bulk of the strap, and figure out the velcro mess in the rear; this will be worth the money.