I've had 3 sets of arthroscopies, although the first two were when I was a student. The most recent one I was signed off for two weeks, and for the first few days I was off my face on painkillers. I actually worked from home during the second week (my choice, trying to get promoted), although I did still feel occasionally a bit trippy from the tramadol. Weeee!
Truth be told, I could have done with another week of working at home, mainly because I wasn't allowed to park in the company carpark and the normally 15 minute walk turned into a rather sore (I had both knees done!) 30 minute trek. -_- As mildly annoying as I found that, the OP's boss sounds like a complete and utter ****.
I think a lot of it will depend on the individual - everyone has slightly different recovery times, or different responses to painkillers. Just do what the doctors tell you to do, and make sure you do your exercises!