The rheumy is probably the best person to see about this. They diagnose IBD related arthritis by ruling other things out, in particular lupus and RA (for RA, they look at both the RF, and anti-CCP). If negative for both lupus and RA, at least in our experience, they call it IBD related arthritis. The treatment is pretty much the same as for crohn's (or RA), and one of the first things they want you to try is MTX.
Also, MRIs can be useful in visualizing the joint, to see if there are any degenerative changes, to see if there's some osteoarthritis going on as well.
Our rheumy basically wanted to rule out osteoarthritis in the joint, RA, and lupus before proceeding with treatment. She said that if RA was positive, she'd want to treat it aggressively before it can do permanent damage. But with IBD related arthritis, she said we have more time to bring the flare under control, because rarely does IBD related arthritis cause permanent joint damage.
I hope you're just having a touch of crohn's related arthritis, if anything. Keep us posted.
Husband with Crohn's
Diagnosed March 2003 Ulcerative Proctitis
Diagnosed March 2008 Crohn's & C-diff, hospitalized 45 days
Canasa, Lialda, Remicade, VSL#3, Florastor
In Remission since June 2008
Stopped vancomycin for c-diff Jan 1 2009
C-diff free, until Sep 2, 2009
Fighting c-diff, I guess for life