I Had TKR On My R. Knee 4 Weeks Ago.

I had TKR on my R. knee 4 weeks ago. I am 70 and have always been a very active person (except of course 2 weeks prior to and since the TKR surgery). I do my exercises daily, walk with a cane whenever I can, I have a physical therapist come 2 times a week, he says I'm doing great and an R.N comes 1-2 times a week for my vitals, so far everything looks very good. So when can I drive?