Oh boy, I wish the PT hadn't said that without knowing for certain what transpired.. I would have froze right in my tracks, too.
I had tenacious swelling with my right THR.. the worst case I ever saw first hand was on my poor mother, it was relentless! I could move it and then she would complain about needing to pee all night.. but it would return the following day after her rigorous PT.. she was in a skilled nursing unit for her recovery so OT was a huge part of her days, unfortunately I didn't know about our right to say no thank you , not today please. which extended into my knee and foot/ankle
It eventually receded and stayed away but it took her a good 6 weeks to see consistent improvement.
Back to your swelling, though. It could be impacted by your past history with your upper right side. Did you ever have any Manual Lymphatic Drainage (MLD) sessions after your breast surgery? If yes, would you consider going back for some more sessions and treatment?
Your lymphatic might just be a little sluggish and need some "priming"
I see this quite frequently and it's amazing just how quickly the body can respond with a little help in the right direction.
There are things you can do at home, too. I hope you don't mind if I leave you some simple breathing exercises to help stimulate the lymph flow.
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Take deep breaths.. deep, as in breathing in to a count of 3 or 4, whatever is best for you. hold it for another count of 3-4, then blow out completely, still using the count that's comfortable for you. A series of at least 6 of these could help get your excess swelling to move. To ensure you are taking proper deep breaths, place your hand on your naval and watch while taking in your breath, if doing this properly you should see your hand move up.
Then, as you slowly breath out, to the same count of either 3, 4 or 5 gently press down and slightly upwards with the palm of your hand.
Do this whenever you feel up to it during the day or night. The more supine that you can get in the recliner or bed, the more effective this can be.. you have lymph nodes located in your groin and sitting up too much can cause a restriction of the lymph flow.
You can, after the breathing, place your hands lightly on your upper thigh, right where the crease is in your groin and lightly stroke upwards towards your naval.
I did this quite a bit post op and while it takes a while for the body to wake up and respond, it will and it will help get things moving.
The reason this can help is because our lymphatic system doesn't use our cardiovascular system to help lymph fluids move.. no assistance from the heart pumping. Our breathing and our physical (muscular) movements keep it flowing.
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If you have any questions about this, please let me know, would be happy to clarify anything that may be confusing.
The key is to get comfortable on your back with your legs elevated quite high and then do the breathing, etc. It may take a few times to get things stimulated and flowing and it may return in a day or so, but that's okay! Each time you work on it should help.. mine took weeks to go down and stay down but the relief I got was huge for my spirits and discomfort.
Plus each time I went through the routine, I would fall asleep and remain elevated and would wake up feeling better!
There are additional steps for easing any congestion around your clavicular and axillary areas, but hesitate to get into that for now.. especially if you possibly have someone you can go to for a complete MLD session.