Well, I live in Britain, so I ride the English way, which sounds like you are if you're rising. Your knees are meant to be on the horses side, you grip with your knees and your thighs. Your lower leg is not supposed to be round the horse, that is the completely wrong position, and so many people ride that way! I was taught the classical dressage position, it is a lot safer to be in that position when your horse spooks or naps. You may not listen to me, as so many people on this ride the way that we are taught not to, the "knees off, lower legs on". It's a shame really.