glucosamine is a compound which used in joint regeneration.

scientist believed that by taking ingesting one substance and raise the amount of that specific substance in our blood can promote production/joint cartilage formation.

the truth is that it doesn't really work that way, what we ingest is not equal to what our body synthesize. yes, you can take calcium pill to prevent early osteoporosis, but there's a few factors to be consider.
1. absorption - absorption of these substance require "carrier", different substance have different absorption rate, and age is also a factor. you can ingest a lot, but there's always a maximum limit you can absorp.

2. metobolisme- next is the metabolism of absorp substance, many things can happens in our body, metabolisme of these substance often require another compound to bind with...

3. synthesis - synthesis of joint cartilage is not as easy what ABC, it's a very very slow process. one is because the inner part of the joint is not supply by blood vessels, only the outer part is supply by blood. thus this makes cartilage very very slow, regeneration in old people is even slower.
when you have degenerative joint disease like osteoartritis, it's mostly because of your wear and tear of joint out balance the regeneration rate. sorry but to say, it's quite impossible for healing with you reach that stage, what you can do is prevent further damage of joint until the joint completed ruin, and you get yourself a joint replacement.

to make it simple using metaphor,

eating eyes doesn't make your eye see better
eat more heart doesn't makes your heart stronger..
almost same goes to glucosamine...it's better if you go knock off all the joint cartilage when you eat chicken next time