Arthritic changes can happen at any age, puppies at 4 month old can already have arthritis in joints.
My first dog (Mastiff x) was on Cartrophen injections and glucosamine for 8 or 9 years, they did help her joints a lot. I have no idea if it will help with spinal issues but there's probably only one way to find out - the main thing is you need to be patient with the Cartrophen and the glucosamine especially it takes time to work, at least a month until you see a difference.
With Max it made a huge difference, the Vet told me to have her put to sleep when she was 4 years old because she was arthritic and had had surgery to repair a torn ACL - she lived to 12 years old
She did get Rimadyl for the least 6 month because she was uncomfortable without any pain relief.
All my dogs now get a joint supplement with glucosamine and MSM - the older girl because she's 6 years old as a preventative (she's showing no signs of pain) and the 11 month old pup because he already showed arthritic signs in his elbows at 4 month old and had surgery to fix an ununited anconeal process
They are both on a low maintenance dose of this stuff Joint Guard For Dogs - Nature Vet
I would also look into acupuncture like jocoyn said
It worked great on one of my ex race horses that had spinal issues