IBD is systemic and can effect lots of areas beyond the gastrointestinal. Autoimmune inflammation loves to attack the joints (see our contributors takes here: https://inflammatoryboweldisease.net/living/crohns-joint-pain and here: https://inflammatoryboweldisease.net/living/uc-joint-pain).
Rheumatologists have extra training in dealing with autoimmune joint issues. Have you ever seen a rheumatologist for joint issues and was it helpful?