Sending along some good luck vibes for whatever you choose to do.
Have you thought about swimming and water exercise as an alternative. It would be much easier then an exercise bike. You will get the resistance you need to strengthen the muscles, plus you are a lot less likely to cause anymore damage.
Also if you have access to a whirlpool or hot tub they go a long way in helping to relieve the pain associated with osteoarthritis. Also keep in mind that the cortisone not only relieves the pain but also the stiffness so your less likely to cause more damage.
I have cortisone in both my knees about every ten months..and it has been a god sent for me..
I don't have access to a hot tub either but with our newly remodeled bathroom, will soon have a bathtub that works again as more than a place to stand while showering and I plan some glorious bubble bath soaks
If you don't mind my asking, are the cortisone shots painful? Per my PT, and his patients, they are. If they are, I'm likely not to get one unless I can't sleep/move around etc.