As you might know, I used to have a health food store. I have personally seen enough before/after transformations to be convinced that glucosamine at the very least puts a smoothing coating over pitted joint surfaces.
I first heard of it long before I had any interest in nutrition, on Towards 200/Quantum/Catalyst/whatever incarnation of {this science show I respect} they were on at the time. That had to be more than 20 years ago. That show was specifically about shark cartilage, the percentage of chondroitin in that form of glucosamine is very high. It's gone downhill recently, but in its early days it was well researched.
When I opened the shop it wasn't long before people began to ask for glucosamine, on the recommendation of their Dr., and I had to get some in and read up a bit.
I saw some amazing transformations in the next 10 years. My favourite was the 82yo man who couldn't bend to pick up 10c before, but came in especially to show me and got down on his knees in quite sprightly fashion to illustrate the difference it had made.
Then I had my own experience with it. I was prescribed a drug for something else entirely when I was an active 53yo with just a buggered right knee, that had the unwanted side effect of loosening off all my ligaments. That meant that all my weight bearing joints were grinding in ways they weren't meant to and the other joints were doing things they weren't meant to, as well.
I stopped taking the drug and my ligaments slowly tightened up, though there is still a bit of slack in most of my joints, but a lot of damage was done and the pain and stiffness remained. To my shame, it took me more than a year of walking past glucosamine 30 times a day and advising others on the correct way to take it, before it occurred to me that I was a candidate.
I took my own advice. I take a total of 1500mg a day, plus at least 300mg of chondroitin and make sure I get some vit C every day, in tablet form if necessary. The brand I favour has the sulphur etc.that you mention incorporated.
Like you, I would like to see some formal studies. For myself, I am getting steady improvement but notice the difference if I am away from home or forget it for more than 3 days. I have also learned not to switch to a type with less than 200mg chondroitin. The economy isn't worth it.
What I gleaned from my reading and experience: Oral Glucosamine will deposit on joint surfaces but needs the presence of Chondroitin in most people. Chondroitin seems to help you produce synnovial fluid but I ran into people who COULDN'T take Chondroitin because their joints swelled and became unbendy. I would love to know if this was some sort of allergic reaction or a variation on the pressure suit phenomenon.
I don't believe for a minute you get the joints of your youth back, but it does seem to paper over the cracks. I have seen too many astounding increases in mobility to be able to dismiss it.
If you find any studies that have examined joints after extended use, either arthroscopically or post mortem, I would be interested.
