@Honey007 .... you were smart to keep the Pelaton at it's lowest setting (I'm assuming that means no resistance). But starting with 20 minutes was the problem. With knees - even those that are well out from surgery - you need to begin any new exercise or activity very slowly.
Go back to babying the knees for a bit with some Tylenol for any pain, rest, ice and elevation. Once the pain is gone, start again, but make your first session just 5 minutes. Wait a day and see if everything is okay. Then you could try 10 minutes. As long as you're giving yourself a day in between and there are no problems, you can add time at 5 minute increments every other day. Once you get to 30 minutes, you could start filling in with some time on the "off" days. But again, go slow until you get to the point you're doing 30 minutes a day with no pain afterwards. Approach any further increases in either time or resistance the same way. If at any time you get pain the next day, it's your body saying it's not quite ready for that level yet. Back off for a while and try again in a week or so. These things take much more time than you think sometimes. Your body will let you know when and if it's okay to proceed. Right now it's telling you - noooooooo.....not that quite now!