Actually, my joint pain goes away when I'm on remicade. That's why I'm such a big fan of it. My typical flare is a couple days of stomach pain, followed by several days of severe arthritis. It's totally inconsistent where it will show up though, could be my hip or knee, but usually either foot or hand/wrist.
Allison, a better explanation than I can give for the joint pain can be found at the wikipedia article on crohn's (under extraintestinal symptoms) but basically it says the hyperactive immune system that causes crohn's can also result in joint pain. It's kind of like running a car at 17K rpms, yeah, you can do it, but doing it for too long will eventually tear the car up.
Anyway, people with Crohn's is not strictly true rheumatoid arthritis, although many of us may consult one, but the distinction is really only relevant to the lab coat types.