Exercise question

I'm still pre-surgery, but I'll chime in anyway! I love the rowing machine. I feel like it's a good all-around cardio workout for me - I feel it in my arms, legs, and core, and it definitely gets my heart rate going. The resistance is adjustable so if it's a day when I'm feeling particularly sore from weights the day before, I can back off the resistance a little bit but still go at the same speed for the cardio benefits. They're also not outrageously expensive if you'd rather work out at home than in the gym - I bought mine for less than $250.

I joined planet fitness, basic is like $10 a month. I have torn meniscus in my knee. Therapy told me to never get on a treadmill again (unless I have surgery to fix it) 

best exercise that doesn't inflame my knee has been the recumbent bike. You sit in it like a chair. The angle is different than a regular bike and it has allowed me to get up to 4.5 miles in 30 minutes :)