Hi, and welcome to our family.
Well I'm going to give you a very different response than the others gave you. While "arthrofibrosis" has an incidence of maybe 1% or 2% or thereabouts, it is a common reason people find this forum.
I've been where you are. I left the hospital with 85 degrees and got worse ROM with my efforts. I don't know if it's true for others who have arthrofibrosis, but because of my limited ROM, I was pushed, had more pain than average to start with, so I was quite debilitated by pain and poor mobility and a lot of swelling. I knew something wasn't right.
Your ortho will assess your situation, figure out what's holding you back, and most likely propose a solution. The good news is that if it is indeed arthrofibrosis (which your description seems to suggest), of all the complications, this one is minor and resolvable (look at my signature). Infection, which also has an incidence of about 1%, is a nightmare by comparison.
As others have said, go easy, ice and elevate, and see if you can be any more successful than I was at being patient. It's hard to be patient when one has undergone a major surgery and finding that the promised results are not manifesting. They will!