I think you guys are both right. You can't absorb much of a landing with folded knees...certainly can't go as big as you could on a snowboard or skis. Don't let that complete your judgement. Sledding is one of the most fun things i've done in my life. It's a completely different concept compared to snowboard, but that doesn't mean it's not fun or that you have to choose one or the other. If you're gonna hit a jump on a sled, you just need a good, soft landing. Try it, then let me know what you think. My knees are fine.