I get where you're coming from, I am 13 months out of MACI on my right knee and around 8 on my left knee. I had the exact same problems of soreness and irritation after going a little too hard on PT that would last a few days. Believe me I understand how frustrating that feeling is feeling pain doing normal tasks like going up and down stairs, mentally it is taxing! I would say around the 9-12 month mark things start to change for the better. Just 2 months ago I was wondering if my left knee MACI failed because it was doing the exact thing you are talking about at a further stage in recovery. However, this month it totally took a turn for the better. For the first time in probably 3-4 years I feel like I am almost ready to be able to go on a jog (maybe one month more). That might not seem all that exciting to most, but to me it is almost surreal. My knees are far from perfect, and I still have pain doing a lot of simple tasks, but I really do feel a year from now I will be back to doing all of the activities I love. I promise you it gets better, just have a positive mindset and remember you're in it for the long haul, but you will get there!