Arthritis in dog?

Hi all - my 8 year old pitbull is slowly starting to become a bit stiffer and visibly more sore after longer walks / more intense exercise.

Yes, we’ve been to the vet and nothing notably wrong can be found and given the fact that this has been pretty persistent for the last ~ 6 months, the vet is suspecting onset or some mild arthritis.

Anyways, this guy LOVES to walk and would walk until his legs fell off… literally. There have been a few times where he seems to have an extra pep in his step so I extend his walks, only for him to start getting a little gimp towards the end.

Does any one have experience managing arthritis in a youngish old dog that still wants to be relatively active?

I want to let him play but I also don’t want it to result in him being uncomfortable later. 😓