I've had six arthroscopies-- three on each knee, a broken knee cap, and now, one replacement.
I was on crutches for only a day or two after the arthroscopies, but I got my quads really strong before surgery. What led me ultimately to replacement was the broken kneecap. The pain was unbearable and now I do the SF to LA AIDS ride every year.

Other than the orthopod you are seeing, if he isn't strictly a sports med guy, I recommend you see one. My first orthopaedist thought all women did was shop, but then I found someone who really understood my need to be active.