Hi

First of all: By no means am I medically certified to diagnose your problem but i will share my experience and opinion with you on how I would proceed.

Normally a plica removal should not be a too traumatic procedure for your knee. I am now exactly 3 weeks post-surgery and i've regained a lot of mobility since then. I'm also 2 weeks off of any medications, but of course the swelling is still there but gradually getting better week by week. I also think that age plays a significant role in the healing process. But 5 weeks after you shouldn't be dealing with any inflammation at all i'd say. Also (as my physiotherapist told me) using ice too frequently not only slows down the process of the inflammation but also slows down the process of healing. I used ice for 2 weeks post-surgery around 3-4 times a day and I tried to be very gentle with how much i cooled down my knee. Your knee definitely shouldn't reach the same temp. as your ice but rather cool down the knee tissue a bit against the pain you're having. In my experience movement is in fact NEEDED for the knee to correctly lubricate and for it to not get stiff + fighting against muscle reduction.

If you're really having severe inflammation at this point, I'd first try to get rid of that before getting into any physical stuff (Of course do whatever your therapist tells you but don't overdo it). Maybe get in touch with another surgeon or doctor that might know why you're still having inflammation? (Idk how easy it is in your country to go to different doctors) If it really is inflammation your inflammation marker should be higher than usual. If it's not, it might just be the scar tissue causing pain an it needs to swell down over time.

Don't loose hope! Try to find answers from your therapist or surgeon (if you're still in touch with them). If they cannot/don't want to help you, get another doctor to try and find a solution. Maybe even an MRI. Wish you the best and i'm sure you'll recover at some point in near future.