I have taken Januvia (brand name) on two separate occasions. It didn't seem to do what it said on the box on either occasion but the second time it seemed to make my BG control much more difficult, at least my FS Libre showed BG readings that were all over the place. I also just didn't feel right, and not able to put my finger on exactly what was "not right".
Personally I didn't feel any joint pain but I must emphasise "personally". It will affect others in different ways as we are all very different. When talking about my personal experience of any drug I would like to draw your attention to my signature below.
I have been taking sitagliptin for about four years now and no side effects.
I did get the aching leg pain when I tried statins
Have a word with your GP, he or she will either change your meds or give you an alternative.
There are other glucose lowering drugs available and also other gliptins.