Hi, I didn't have the arthritis to start with, but I did develop tenosinovitis in the wrist, at the base of both thumbs. My medical oncologist changed me to exemestane with a slight improvement in these symptoms. I have also, at different times, developed trigger fingers, which sounds a bit like what you're getting. All this can be aided by steroid injections, and splinting to rest the joints. When do you see your med onc next? Don't let anyone tell you it's not related, but there are good management strategies around. My med onc wanted to change me to Tamoxifen this year, but I said no, prefer the devil I know!! I have another 2&1/2 years to go, to my 5 years of AI. That is doable. Longer? Don't think so.
Talk to your med onc. Sometimes you'll get side effects with one AI, not with another, so it's worth a conversation.
Oh, and I didn't start getting any side effects until the 4-6 month mark.
Take care