I've had two series done - and I don't remember the name of the stuff - it was derived from rooster combs
I think it helped - I had it done in October 2006 and November 2008 - Medicare paid for it, but without insurance, I think the injections were about $500 each - and I had a series of three each time.
My knee was more like uncomfortable than seriously painful - the cartilage/meniscus is very thin. The big difference that it made was that it was a lot less uncomfortable at night. I could stand to have my knees touch each other again when I sleep on my side.
I also take Shaklee's Joint Health Complex which my husband also takes. Mr. Doubting Thomas thinks it helps him, too.
So - for me, I think it was helpful. Of the six injections, only one time there was a tiny bit of bruising. The other five times, only minimal discomfort while being injected, and barely any after discomfort.