First, good luck tomorrow, Parman. Best wishes for an uneventful stay in hospital and recovery.
Regarding leg exercises, before you are cleared to go in the water, walking remains the best exercise, as I know you are very aware! Also, I would do very simple isometric stretches with the leg -- do it with the back supported, while in bed or lying on the couch or floor, just to be sure you aren't affecting the spine in some unintended way...and just tighten and release the muscles of the whole leg. You can flex and point the toe as you think about tightening the muscles, and you can hold each position for a bit.
If you are cleared to go in the water, find a warm therapeutic pool and just walk. Don't worry about doing any stretches or exercises in the water. Just walk back and forth in the warm water. You can walk forward, backward and sideways where you step to the side and then bring the other foot together with the first foot (not the cross-over type of sideways walking...not yet, anyway!)
I had a 3 level fusion from L3 to S1 in June and have just recently been cleared to go to the pool. Most patients are allowed to start a couple weeks after surgery...for simple walking...but I had major spine reconstruction and my surgeon is not allowing me to take any risks, small though they might be! Anyway, the instructor just had a two level lurabar fusion in July and she is back to teaching the class!! So I am just passing on what she suggests for me. She said she recovered quickly by just walking, walking, walking in the pool...forward, backward and sideways!! (By the way, just for a chuckle...she's the one who point blank told me "You need to find a BETTER doctor" when I was introducing myself at the beginning of class and said I had just had a 3 level fusion, my third surgery....Then she discovered we shared the same surgeon!! The look on her face was PRICELESS.)
