We use these, the UltraCrash pads, which are pretty much invisible under a pair of pants:
http://www.skatingsafe.com/They work amazingly well; a 150 pound skater can fall out of a triple jump onto a knee and not feel it. Plus, the ability to "pick your spot" in terms of where you need it, i.e. there are specialized ones for tailbone, hip, knee etc. Other big advantage, you can use them with any pair of pants, including LuLu ones; actually LuLu pants work great with them, so do Chloe pants and UnderArmour frosty tights.
And, yeah, they're hygenic and easy to wipe clean ... which I really like ... no padding or material for body products including but not limited to sweat and blood to leak into ...