85 year old torn meniscus in right knee, pain/inflammation when walking. Recommend hyaluronic acid joint injection? Other non-surgical therapies?

If your joint is in- -good condition, a menisectomy would be advised, even if borderline. This can slow down further degeneration & possibly avoid a replacement. Hyaluronic acid if the joint is bad & the only option is a replacement, if you are one of the people that get great results, you still may avoid a TKA. If successful they do need to be repeated over time. .