Jo is away for a short while, she will be back soon. I am struck by your posts----I also had pain from overuse and frankly, I had trouble believing that the amount of pain I had was from overuse, but it was.
So, despite swelling, you have continued to shoulder on---walking too much, going back to a strenuous job, doing pt, etc. Now, we tell you that this level of activity can cause swelling, but I am not sure that you believe us.
In fact, I tell people to deal with the swelling early on--to lie in bed 80% of the time during the first 3 weeks with their leg elevated and icing non stop. Just so they do not incur the problem you are dealing with now----chronic swelling!
You are very knowledgeable about the muscles, but you want to "work it out"---it seems that rest is not an option for you----and yet, in my opinion, your body is crying out for rest!! Try an experiment. Take a weekend off----Stay in bed or on the couch the entire weekend---getting up just for bathroom breaks and meals. Have a good supply of books handy. Elevate your leg the entire time and keep ice on it too. Rotate two gel packs.
Elevating your leg to control swelling and pain
Using ice
Do not walk those days, do not work, do not go to PT. Now, how does your knee look? If your swelling is down and your pain is less---you will have your answer. I think you are going to have to limit your activities for a month or so---not the rest of your life!!! you need to take care of the swelling by icing and elevating for hours when you get home from work--not 20 min. Your chronic inflammation is going to need to be treated by RICE--rest, elevation, icing and compression.