Unfortunately there is no 'supplement' with any decent evidence supporting its
use for 'joint health' or joint pain related to degenerative changes.
Bone health (density) is a different topic, as are autoimmune disease affect the joints like rheumatoid
arthritis.
The only things that have helped me are the boring stuff like building up mileage gradually
after a hiatus, taking easy days 'easy', supplementing with biking, getting enough rest, etc.
I have some patients that swear by glucosamine/chondroitin but I suspect it's more of a placebo effect.
In the near future there will biologic agents approved for osteoarthritis but I don't think they will be applicable
to the average runner in their 30s-40s