Bruising - I have to think that swelling, the healing process, and some alteration in blood pressure in the surgery area results in various capillaries here and there being broken. I can't think of another explanation as long as there is no new trauma. I had very little bruising at all but I did have some swoled up leg days.
"There is no real answer to this question as it's different for every person. We don't mandate a specific number of steps or distance. You have to listen to your body's limits all while working to ensure that you are progressing over time."
This is pretty typical orthopedic dr talk I think. They aren't going to take much responsibility for our healing process. What they are going to do is set boundaries and expectations, & presumably you're inside of them. You might get a better reading from a very good PT. I set my own limits for a while & used a fitness watch to keep track.