On Mar. 1st, I Had 6 Stents Inserted Into My

On Mar. 1st, I had 6 stents inserted into my heart arteries, 4 in one and 1 in 2. I want to know more specifics about aerobic exercise, such as by what percentage or number of beats one's heart rate should increase to qualify as aerobic. Also, I have serious osteoarthritis in both knees. I'm having trouble identifying aerobic exercises I could do because of that condition.