Conundrum

We're all faced with them, right?
Here's mine:
I can only walk for exercise now. Well, that & ride my NEW BIKE, but whatever I choose, I may pay a price with my right knee in terrible pain afterwards.
Yesterday on my (late) lunch break, I walked 2.4 miles, all over town. ALLLLL over town.
My knee, the one I had surgery on in October, is paying a price for that exercise.
But when I exercise like that, I sleep so well. And as a lifelong lousy sleeper, it's such a treat for me to sleep soundly.
And I generally feel so much better after a good bout of exercise.
Here's the question: Do I go ahead and push myself, knowing that uncooperative knee is going to give me a problem, or do I become a sloth and do nothing for fear of the pain?
Ha! I think I know my answer, and if you know me at all, you know my choice as well.