Personally I don't know about the large breeds, I have only med. to small dogs. I like to give gluecosamine treats to my poodle who has a slipping patella. I would try to contact the breeder you got the dog from and ask them. Good luck
I have a Mastiff/Rotty mix who is about 14ish months, best guess, he was about 7 months when I got him last April, and I give him Glucosamine and Chondroitin every day to help him with his joints. Being a mixed breed that I was given, I have no idea what the health of his parents are so I am always worried about joint issues.