There are many different types of exercises to do before knee surgery. The trick is in HOW you do them. Do you repeat the same movement over and over? Do you zone out as you 'get them over with?' Do you do them while watching TV or talking on or looking at your phone? Whatever you practice, that's what you'll get good at. So if you practice moving while 'zoning out' . . . you get the idea. 
So, let's look at what's going on when you zone out. Can you do it right now? take a moment, zone out. 

How do you do that? What are your eyes doing? where are they focused? are they turned inwards? is your jaw tight or slack? are you sensing your contact with the chair? how are you breathing?

Now, keep asking these same questions, and direct your eyes to look somewhere in the room other than the computer screen, so that you are attending to the sensations inside you, as you simultaneously take in your surroundings. 

Are your eyes working differently as you do this? Are you 'seeing' both outside and inside of your self?

Now, begin to look down towards your belly button, very SLOWLY. If you lose this sense of seeing 'outside' and 'inside,' return to the start position, PAUSE, then slowly look down towards your belly button. The 'inside' will include the sensing of the front of you shortening and your pelvis rolling back. The 'outside' will include everything in your visual field as your head and eyes lower. Continue practicing this, breathing out as you look down, in as you return to looking directly ahead. Now reverse that to breathe in as you look down, out as you look ahead. Go back and forth, reversing your breathing, so that you can sense which way is easier.

Now, get up from your computer, and sense how your feet are making contact with the floor. Walk around a little.

If you practice bringing your full attention to your movements, you will move with less effort and coordinate your whole self in all you do. Continue practicing zoning in and out till you can be in either state any time you want.