I don't know what CRP really does, but I thought it measured inflammation in general. If that's the case, then it could very well be your joints.
Either way, if you don't feel bad, I wouldn't take it. Maybe up your asacol first? I know the docs are trying to keep the inflammation down so we don't get cancer. When I was feeling ok my doc told me I needed to stay on the asacol, or whatever she was pushing at the time, to keep down the inflammation I couldn't tell was there. I opted not to since I was pg and I thought that those mesalamines were making me ill (ie, could be causing the inflammation).
If it is your joints, the azathioprine might work systematically and help with that, though I agree it's not something I'd opt to go on either if I was feeling fine.
dx 4/05 with pancolitis UC after birth of my second child...
18 months of vit e enema and scd remission
Flare since 7/07...almost to surgery, now almost well through mostly natural stuff
Trying to make up the difference with...
Lialda 4/day... I don't know, 3 months maybe?
Remicade 10/26, 11/09, next 12/3
Imuran 50mg at night 11/11
Been there, tried that....