I have been taking glucosamine for many years. The ironic thing is that my surgeon years ago mentioned that my knees were too far gone for it to help. Ironically I followed his instructions for quite some time, until I also had to put one of my dogs on it. The vet(also a friend) suggested that I try it... if it didn't help then obviously stop taking it. I did start to take it (once to twice a day) and it did help, and quite often will remind me if I for some reason I have missed it for a few days. Now it is NOT going to rebuild the cartilage that I no longer have, but it does indeed take away some of the pain/irritation and living in a 3 story house I'm thankful for that.