I read a lot about this being a training issue, but I have played some ball myself and I can't imagine that it's really possible to train a player to avoid knocking knees (especially a Center). As strong as these guys are, they probably would have stronger then averages knees even if they didn't play ball, so I doubt you can get their knees that much stronger without seriously effecting their ability to jump and move laterally.
Even though the blazers are taking the brunt of it, the knee problem is probably a league wide issue. Look at Blake Griffin for example. Players in the NBA are getting so strong and quick these days that anytime one of these guys cuts to the hoop, a Center who gets his knee involved with trying to stop them is taking a pretty big risk.
It seems as though wearing kneed pads could help soften some of these blows and reduce the possibility of serious injury? I know it might sound silly but probably just as silly as the idea of wearing helmets in football before that started happening. Didn't they used to wear knee pads in early NBA days? I mean it probably wouldn't stop an ACL tear from occurring (ala Pryzbilla) as that's usually cause by the knee getting hit at some weird angle, but at least it may reduce the possibility of a micro-fracture (ala Oden)
Any trainers out there have any opinions on this? I would be curious.