For knee
protection, there's a ortho doc on a few websites, Dr. Mark I believe, who recommends a neoprene sleeve/wrap (improved stability) and knee "cup" protection over that. Several mfgs offer products as separate items (wrap and cup) and that combine the two. Inexpensive. From the way you described your incident, the cup sounds like it would've helped.
If you inquire about knee
braces you'll see a variety of opinions concerning the types of injuries they prevent. I wear one on my left knee for increased stability because my ACL is almost all the way tore (surgery scheduled in late-September). It is a neoprene wrap with built in hinges on the side, $18 from Walmart. I also use a cup/shin guard unit as well. Sort of bulky on my left knee. I know EVS offers a knee brace of this sort with built in cups and shin protection all in one unit. I'll probably invest in a pair of these, pricey but they look comfortable and it's all-in-one package.
In the link below, page 534 shows an example the cup/wrap, page 533 an example of the knee brace (SX02 was the one I was considering)
http://www.powersportrider.com/cgi-bin/zcatjpg
If the link doesn't work right, choose "Apparel" catalog and then go to "Protection" section. Then browse around.
There ARE other mfgs that offer these products . . . look through the pages in that section of the online catalog.