There will be pain, but your medical team should work out a good plan for you to keep it at a manageable level.
One very important way to not have more pain than is to be expected is to be very careful with the list of exercises you will probably get. Most of these are a standard list that everyone gets. While movement is good for your freshly healing knee, that movement must be gentle. Gentle stretches and short walks around your home are all that is needed in the early weeks.
Don’t let anyone, especially a PT, bend your knee for you. Too many of them bend it further than is necessary, which will increase your pain and swelling.
Saying no to therapy - am I allowed to?
Regaining our ROM does not
require forceful bending or painful exercises.
Regaining our ROM is more about Time than repetitions of a list of exercises.
Time to recover.
Time for pain and swelling to settle.
Time to heal.
Our range of motion is right there all along just waiting for that to happen so it can show itself.
In the general run of things, it doesn't need to be fought for, worked hard for or worried about. It will happen. Normal activity is the key to success.