I'll just mention that people shouldn't feel discouraged by the mixed results from glucosamine use. Give it a trial, anyway. I know I tend to prejudge and think "placebo effect" when results are inconsistent (works for some, doesn't work for others). But in the case of glucosamine, I had to rethink because of my vet's advice regarding dog arthritis, and the results for various friends' dogs. Glucosamine really does work for some dogs and not for others, so it is likely the same for humans. I've no idea why; perhaps some component of the user's chemistry affects results.

I'm just beginning to feel the early effects of arthritis in my hands, and glucosamine is one thing I intend to try - though it didn't work for my own dog!