guys, im pretty sure kneebags come from sitting, not walking.
when you sit, especially in tighter styled jeans, your knees are literally 'poking' into your denim. this is particularly true if you're tall and the angle at your knees is more acute than 90 degrees when sitting on a normal height chair.
so, ive found that pulling up your jeans, almost unfavorably high, before you sit will help eliminate this. in addition, get good, heavy weighted denim.