Kimbocats said, "....the rest of the day was on my feet preparing a big family meal."
That is the answer in part--being up on your feet for three or four or more hours--will almost always result in a swollen angry knee this early in recovery. This is basically a 12 month recovery--you are not quite 2 months post op which is about 1/6th of the way through---with most of it yet to go. So no matter how good you may be feeling at any given time, if you overdo even just a bit, the KNEE makes you pay.
It's really a matter of pacing---if you're up on your feet for a couple of hours----then you need to elevate and ice for at least an hour after that. Activities need to be interspersed with rest, elevation and icing. Somehow standing just exerts more pressure on the knees than bicycling, swimming, and a PT session. And often we are doing much more than we realize because we do not count normal everyday activities like getting up and getting dressed, trips here and there around the house, out to the mailbox, etc.
Just living is a form of PT---so if you're up and pretty active at home and doing the PT exercises, riding your bike, and swimming, you are getting plenty of exercise for right now. When your knee stops swelling for any and all of this, you might then think about strength exercises if that is important to you or you really feel you need it. Depends on how athletic you want to be.