are you sure it's spondylosis and not a slipped disc? Spondylosis from what I understand (and having a gsd who had it), is fusing of the vertabraes in the spine, which cuts off the nerves that run thru those vertabraes, when the nerves are cut off, there is no pain, because they have dead nerves..Mine had 1/3 of his spine fused when we discovered it, he was totally normal acting prior to taking a slip in the yard, and xraying..
Anyhow, this was quite a few years ago, he swayed, used the wall to hold him up , would fall over, knuckle under, my vet was giving him 'no time'. I wasn't ready to give up on him, looked up Dr Belfield, and did a little of my own additives as well..I don't remember the amounts (my gsd was LARGE as well, 32" at the shoulders and 125 lbs of lean body)..but I had him on Vit E, C, D, MSM with glucosamine, hylauronic acid, and Rimadyl. Maybe something else, but can't recall now, but the only NSaid I had him on was the Rimadyl .
Anyhow, whatever it was, worked for him, he did a total turn around in about a month, no he wasn't "perfect" and I monitored him closely, but he returned to jumping on the couch and getting on my bed, going upstairs, so that was a "good" sign.
Back then, there was little to none PT's around, so I swam him when I could..not alot, just minimal exercise.
He lived another year and half, unfortunately, he decided to roll around in the backyard, and the fusing 'cracked', so I had to put him down
I would suggest a couple things, look up Dr Belfield, his concoctions are more for dogs with DM, but it's worth a shot. And look up Degenerative Myelopathy , sometimes some of the treatments for 'that' help with spondylosis.
I might add, Kodi was NEVER in any physical pain, because those nerves were basically 'dead', so no feeling..
Good luck to you, it's a rotten disease, especially when the mind is still there but the body doesn't want to cooperate..