It could definitely be arthritis. Some of the common symptoms of arthritis are morning stiffness, pain that gets better with movement and worse with inactivity and swelling or redness in your joints. Heel and knee pain is common in Spondyloarthritis.
CCFA has a good summary of the various types of arthritis associated with IBD.
http://www.ccfa.org/assets/pdfs/arthritiscomplications.pdf
I would definitely go to a rheumatologist if you can - they specialize in arthritis.
If the arthritis is not advanced enough, it would not show up on an x-ray. So I wouldn't just go and ask for an x-ray, necessarily.
Inflammation is not visible on an x-ray, only damage is. So if the arthritis is new, often it takes a while before it is visible on x-rays (years, sometimes). Rheumatologists often use MRI's to see if there is inflammation (usually they will do x-rays first and if nothing shows up, then an MRI, since MRI's are MUCH more expensive!).
Ice, heat, physical therapy and swimming might help with pain while you're waiting.