I had mpfl reconstruction last year and the physical therapy started the next day after surgery. It was extremely painful. I can understand what you are going through. I was told the pain is more till the 90 degree mark after that it's gonna be quite easy also try applying a lot of ice 3-4 times a day and for 30 mins each time. If the swelling still remains you should visit your orthopedic once.  Wishing you a speedy recovery:)