So if you are planning a grueling outing in a theme park following knee surgery, renting an ECV is the way go!! (I also took one of my walking sticks--it was a total lifesaver. Traipsing around WDW would have been impossible without it.)
I was also surprised to find out that I could go through airport security without setting off alarms. I knew someone else who told me to wear pants that I could pull up easily over my knees because he had to show his scars when the alarms sounded. Some doctors give you wallet cards to carry to show to airport personnel, but he was told that anyone could get those cards; they wanted to see his scars!