Hyaluronic acid? It definitely seems to work, better in the joint than systemically but I believe I found it is a possible and likely carcinogen? I forget.
there is/was something that showed hya as potentially carcinogenic, that said i know a bunch of ppl who use it and only get possative things.
i have never tried ia admin, though there is research and info to support it. in this case hya is just a filler.
systemic it is less effective but also working via different method.
it also seems to have an effect on im scar tissue when used im(systemic) and can slow the release of various things when mixed in depot.