I started giving Coco supplements when she was about 9 or 10 (she is 14 now) - like you she had no signs of joint issues but I wanted to preempt them.
She had Yumove for a while, but then I changed her onto Golden Paste - made it myself at first which is easy and now she has the chicken slices from The Golden Paste Company. Turmeric is a natural anti inflammatory and many people and animals have fantastic results with it.
I have heard good things about Yumove too, but better things about GP. She also sometimes has a teaspoon of salmon oil on her breakfast.
So far she shows no signs of problems with her joints and still trots around as she always has, albeit a bit slower now
Lots of info on here about the benefits of golden paste. It doesn't keep that long so, when I made a batch, I froze it in ice cube trays and just took out what I needed for her. If you are on Facebook, join the Turmeric User Group which has loads of useful info and recipes for making the paste yourself.
https://goldenpastecompany.co.uk/