My small/medium sized cross breed was stiff on one back leg.
When I tried Joint Aid for Dogs the improvement was amazing.
I have a noisy and enthusiastic terrier cross (in my household a lively dog is a must!). As I work at stables and have two terrier crosses and a working/showing and racing lurcher, seeing him unable to join in the fun was heartbreaking.
I have always said that the day my dogs cannot run is the day I make the awful decision, as I feel life like that would no longer be enjoyable for dogs that are used to so much exercise.