It's fantastic.
Two years ago, I went in to the ortho to have my right knee checked out. The symptoms were that every time I did anything athletic (running, tennis, etc) I'd have to come home and ice and wrap my knee. It was chronically swollen and tender, but I wasn't going to let it keep me from playing tennis.
I feared a ligament tear or something, not considering arthritis. The x-ray revealed osteo-arthritis in the knee attributed to my being 300+ pounds and still engaging in high-impact sports (tennis and basketball). I had lost a lot of weight and was now able to move quicker, except for my knee holding me back.
Anyway, the option of Euflexxa was surprise to me, but the doc said that he'd used it on his NFL patients and usually bought them a few more years on their careers. I figured, by that math that it could cover me for a lifetime...he suggested at least 5 years of relief.
The injections were surprisingly painless, and only felt like the knee was a little swollen for about an hour after receiving the injection. I was advised that I could resume normal activity immediately. There was immediate relief from the pain and swelling I had experienced previously. The series required three injections over about 6 weeks.
That was 2 years ago, and I haven't had any recurring pain in the right knee at all. No swelling after activity. No need to ice after each tennis match.
I'm sure that mileage may vary based on the damage already done to your knee, but for relief from arthritis, it's worked fantastically for me.
For comparison's sake, at the time of the injections, I was 35 years old, 210 pounds, and the doctor said that I had the knee of a 65 year old.