A knee guard can't protect your knee if it's slipping down your leg. With a strap above the calf muscle and a replaceable Velcro sleeve that mates with the Velcro backed guard itself, these things are practically welded to your legs. Nope, they're not going anywhere... except maybe to the podium after the race.
All I can say is, "Wow!" These protectors from TLD are the bomb! Based on their design, the protection actually stays in place! They aren't clumsy to wear and you'll forget you're wearing them. It's also great knowing you don't need to pull them up to keep them in place every so often. I will definitely buy another pair when mine eventually wear out. 5 stars from me, for sure!