IIRC, about 50% of those taking glucosamine report that it helps, but often it takes a few months to see the difference.
As for "nutritional" supplements - more and more I stick by the old adage "less is more". Yes, hiking requires lots of carbs in the short-term and fats/proteins over the long, but for me it's better to get them in a 'natural' a form as possible. Have found that my body responds just as quickly from the sugar in a slice of dried pinapple as it does from a shot of Gu, and for some silly reason I think the pinapple is a better choice.
But ... the above is a minority opinion based on previous threads. People tend to feel as passionate about food/food-like substances as dogs on the trail, cell phones, GPSs, etc. Your question may generate lots of posts ...