For proper diagnosis, you need to be referred to a rheumatologist. There are a couple of types of arthritis associated with IBD. The most common is a peripheral arthritis that seems to follow the course of the disease, and usually is vastly improved by colectomy. The other is spondylitis and its related diseases. Enteropathic arthritis is the related disease associated with IBD. It has an independent course, more or less, and can start many years before IBD shows up, or many years after colectomy.
I was diagnosed with enteropathic arthritis a decade after colectomy. All my tests were negative (except for inflammation), but she diagnosed based on symptoms and history. I've been on biologics since 2006, and doing much better. Sometimes you need to see more than one rheumy, as some refuse to diagnose without radiological evidence or a positive HLA-B27 antibody (half or more of those with the enteropathic type are negative).
It can be other things too, so that is why the right specialist is needed.
Here is a link to a site which provides a lot of info on the topic. It can help you decide if the description fits you:
http://www.spondylitis.org/about/overview.aspxHope this helps.
Jan