Has anyone used hyaluronic acid, for treating arthritis?

Yes. I use it freqently for persons with moderate knee arthritis. It is safe well tolerated and works pretty well for about a six month period of time. It does not cure anything but i find it works for a few years in an individual. At that point the arthritis has worsened and then knee replacement is usually necessary.
Minimally effective! Some benefit if injected into joints in various forms by a doctor. They do require a series of 3-4 injections per joint, and some benefit, additive with nsaids, showed better relief of pain. However, and this is big: no clinical studies show delayed progression of osteoarthritis, as of yet! losing weight is more effective, certainly for weight bearing joints!