Back leg problems with my black lab?

I find that the first step is an xray. If it is arthritis, then an xray will show you what stage you are in, so the vet can reccommend the meds for that stage. I find that my dogs all had several issues, so what I thought was just arthritis, was other issues too. We used an old bath towel and put it under the dogs belly and held an end in each hand, and lifted the dogs back legs to help them walk. The vet needs to tell you the meds available, and the side effects to those meds, so you can make the best choice. Good luck