What is he prescribing for the inflammation in your joints? Generally if it is peripheral joints (joints other than the spine), Methotrexate works well.
Alternatively, they could up your dose of Remicade or increase the frequency.
Steroids work well and are used for flares, but of course, they're not a long-term solution.
Spondyloarthritis is just like Crohn's - it is a chronic, progressive, inflammatory disease and needs to be treated aggressively to avoid damage to the joints. Both my daughters and my husband have SpA.
My husband was not treated with biologics because they were not available when he was diagnosed. He has a LOT of joint damage - many hip replacements, a partially fused spine, fused sacroiliac joints, a destroyed ankle etc.
My daughters have been treated with biologics and immunomodulators (like Methotrexate) and because of the aggressive treatment, have managed to avoid the kind of joint damage their dad has. They do both have damage to their SI joints, knees and hips (and jaw for the younger one), but it is nowhere near as bad as my husband's.
I say this not to scare you, just to point out that SpA needs to be treated aggressively, to get the inflammation under control as quickly as possible.
CCFA has a good handout about the types of arthritis that are associated with IBD. In some cases, the arthritis flares when the Crohn's flares, and then treating the Crohn's also treats the arthritis.
In other cases, like my younger daughter's, they flare independently and need to be treated independently.
Here is the CCFA handout:
http://www.crohnscolitisfoundation.org/assets/pdfs/arthritiscomplications.pdf
Good luck!!