To protect your knees while ice boarding is crucial. Last season I borrowed my sons hockey knee pads. Great protection but they felt a quite clumsy (and smelly; ).

Troy Lee Designs Lopes Knee Guards

661 Riot Knee Guards

Down-hill kneeguards for ice boarding

I have used MTB Downhill knee guards quite a while now. Slimmer than hockey knee-pads better ventilated but still providing same great protection for your knees.