It's good that you've set yourself goals Link, and by getting up and doing something you're already doing a lot better than other people around the world. Look after your knees, please. Knees suck when it comes to injuries. If pain persists or if it gets worse I would highly recommend seeing a specialist doctor about it. I tore the ACL (anterior cruciate ligament) in my right knee back in late 2011, resulting in reconstructive surgery where I now have a synthetic ligament in my leg and some titanium screws. I'm totally Adam Jensen. "I didn't ask for this..." Well, I kinda did. What I would recommend is set yourself a plan with your walking and with your calestetics. It doesn't have to be much... it could just be, I dunno... on this day you're going to try and walk <this distance>, you're gonna try and do this many push ups, sit ups, squats etc... then maybe two days later, try to increase the load to go higher. Give it a go if you're not doing that already.