It is probably not unlike a cortisone injection ... i can' t be sure since my cortisone injections were done literally behind my back (in my spin ... another story)! Well, they hurt like childbirth ... of the knee ... if you can imagine that, but as I understand the theory, the substance is like that of the natural synovial fluid which, together with the cartilege, protects and cushions the joint. They actually called them "rooster comb" injections because originally that's what was used because of the similarity between the material in the rooster comb and our own synovial fluid. The synvisc is a gel. They numb you up well and after the injection I had no pain or side effects whatsoever. Of course, they worked so well, I put off my replacements for 4 years ... not a course I would recommend!! So, temporary pain for significant relief ... at least for me. All our situations are different, so your OS can best guide you. Good luck.