Sorry to hear your daughter is suffering, UC is just awful and worse still when it's a child.
When i hear about
leg pain, i often worry about
blood clots which we're much more prone to as UC patients. Deep vein thrombosis (dvt) is the most common of those, effects the big blood vains in the legs, and is always worth testing for an eliminating as a possibility.
I don't hear of sulfasalazine causing pains, and sulfasalazine is actually used as a rheumatoid arthritis drug itself. Usually when i hear about
drug caused pains it is usually biologics that are blamed (like humira or remicade). I understand eliminating her drugs temporarily but if you see no improvements within 48 hours, i strongly suggest putting her back on her medications. It's cleared from the body pretty fast once you stop it. As anything drug-induced doesn't take long to go away once the drug is stopped.
We can get various arthritis pains regardless of age (especially in the base if the spine and big joints within our bodies) . UC is immune-caused inflammation within the large intestine and arthritis is immune-caused inflammation within the joints. The CCFA has a good document on it
www.crohnscolitisfoundation.org/assets/pdfs/arthritiscomplications.pdfWe can get another immune disorder like rheumatoid arthritis. Sometimes immune disorders come in 2's and 3's in about
20 percent of UC patients.