I was in pretty good shape before surgery, but was given some specific leg strengthening exercises to do in the 3 weeks prior to surgery. Afterwards I faithfully did all the exercises given to me by the PT people. Hard, sometimes painful, time consuming, and boring - BUT they work. Best decision I made was to get a temporary membership in the wellness center of a retirement community. They have a salt water indoor pool, geared toward seniors with wide, shallow steps and handrails all around the inside of the pool. Water makes it so much easier and less painful to do the bending and stretching of the knee.
I am now almost 10 weeks post surgery, and I still have residual pain in the knee, especially at night. Not terrible, but not fun either. Also, in spite of the fact that I can easily do really deep squats - butt almost hitting the floor - when it comes to everyday activites like trying to pull a tight sock off the repaired-knee leg while standing, the knee still does not bend as I would expect it to. And lastly - does one ever get used to the really weird feeling when trying to kneel on the new knee joint?