These knee and shin pads from Dainese have a very similar design to their classic downhill pads. They’ve been updated, but there are no drastic changes. Two straps on the shin and one above the knee secure them to your leg, and they don’t move much once they’re on.
There is some movement when you move your knee more than 90 degrees, but it’s rare that you’d bend like that while riding. The plastic protection on the shin stops pedal slaps nicely, and the pad stays in place well when you fall off too – there is some minimal rotation from impacts, but it still keeps your shin and knee protected.