This is a great news - you are doing so well!!
After every bone surgery (knees, hip, shoulder, spine, etc) arthrities sets up in that area. But you can get this condition regardless and most of population does with age (it can start as early as 25). But let it be your worse problem; they have so many meds now to bring that pain and inflammation down. So i would not worry about it now.
Just want to answer to your comment about nighmare stories: back surgeries are very different. I have a friend at 75 who had same surgery you had and he is bending, walking from 2 weeks after surgery and says that he has no pain. No walker, no cane - he is perfectly fine.
But there are more comlicated and extensive surgeries with a lot of hardware and plates, with a lot of permanent nerves damage in a legs and feet, etc. Where it takes a year at least to recover and sometimes people never recover.
Therefore you hear about so many people in so much pain. And i am not talking about old and shapless people here: a lot of us used to be fit, in a good physical shape, full of life, working,etc...
Keep doing a good job and enjoy your painless life!