Bow, if you want to introduce glucosamine into Fidget's diet to help his joints, there are a few ways you can try this - my Toby (who is 12) has arthritis and Glucosamine really does help him.
The bull-by-the-horns approach is to give Fidget a Glucosamine supplement. There are various forms of this, some of which can be put in the drinking water or sprinkled on / mixed with wet food. Unfortunately the problem with this is that some cats don't like stuff put on or in their food - as is the case with Toby. There is also a capsule version, which I use to pill Toby with and he does really well on it - it's made by Denes and is a mixture of Glucosamine and Green-Lipped Mussel extract.
Otherwise, if you don't wan't to go down the supplement road, Royal Canin do a dry kibble called Outdoor 30 which has glucosamine in it. I feed it to mine, but I mix it into their regular biscuits (Perfect Fit / Purina One) rather than feed it neat. It gives Toby just that little extra boost.
Hope this helps.