Hi undencem, I think they worked differently for different people but have worked wonderfully for me. In my 30's I was off the bike for nearly 2 years due to osteoarthritis. I spent a year doing consistent rehab. Ultimately, Synvisc got me riding again. My doc says I am her longest running patient as apparently it does stop working for some. I have been getting shots for over 10 years though. The protocol is a series of 3 shots on 3 consecutive weeks. There is a 1-shot option, but my orthopaedic doesn't think it is as effective. Please note that many insurers will not continue covering after 3 years. I get a series of 3 shots basically every 6 months as that is what is allowed.
Good luck in your recovery.