Almost all of them are modeled to be two handed! This is evidenced by the pommels that they have. While Troikas seem like huge offenders, Caliburs have fairly large pommels as well, meaning that they would make good two-handed swords.
Who's the noob in charge of teaching us knights how to wield swords? I have a complaint to make!
(Should this go in Arsenal? I don't think so, because I'm more complaining about the animations. However, you could say it's a problem with modeling, but I don't think that's changing.)
I think us knights just have really big hands. The grip pretty much fits in one hand only.