Pumpkin is still on BoneSmart and is a Moderator, but she's not the person you're thinking about who mentioned this surgeon. Here is the post you're referring to:
@RunA42K isn't on the forum much anymore, but I've tagged her just in case she still gets email notifications of tags. When you have something like this you want to find, remember that the forum has a search tool. I just typed in the surgeon's last name and it popped right up. It never hurts to get a consultation withe a good surgeon when you're having challenges, so I suggest you go ahead with that plan.
You could try the ultrasound treatments, but I'm not thinking it will really make much of a difference for you. As you found during that 4 days, slowing down your activity and exercise is likely going to be the best thing you can do. Four days -- or even 4 weeks -- could still not be enough to keep things settled down. This is a chronic problem for you and it could well last for a very long time. Sorry to have to tell you that, but there are no quick fixes for a stiff knee after a TKR. It may be that you need to do no more exercising than 30 minutes in a day for an extended period of time.
While it may not seem like you did all that much with a 50-minute walk around the lake, remember that walking outside is more challenging than walking indoors or on a treadmill. You pretty much doubled your time all at once and that is what caused your problem. Your body is telling you that it's not ready for that right now. As long as you're moving around frequently during the day, it really isn't necessary that you "exercise." When the days are gorgeous, go for a 15 minute walk to somewhere and the 15 minutes back instead of the bike or treadmill. Or find a place to sit outside and just enjoy the weather. Or take a drive with the windows open (or the top down, if you have a convertible). Plan a picnic lunch with someone - or just take a fast food sandwich to enjoy in a nearby park. Sometimes you have to find creative ways to get the same results (like enjoying great weather) you would get from your old habits that involve extended periods of exercise.
Cortisone injections are for inflammation and it's usually not a good idea to do anything like that because of the risk of infection.
You really need to ask a surgeon both these questions since this is the person who will have seen your images and medical history and can give you a better assessment of what to try, if you want something beyond what I'm recommending with an exercise and activity moderation.
I know all this is frustrating for you and you want it to just be over. We'll always be here for you to vent and ask questions. Believe me....people here understand what you're going through and will support you.