I was diagnosed with medial plica about 10 years ago. My presentation was very similar to yours. I trained through it for a couple months to finish my first Ironman and it continued to get worse. Ultimately, the orthopedic surgeon convinced me he needed to operate on it to remove it. I was obsessively diligent with recovery, gradually returned to biking/running, and the pain came back, worse than before. I took years off triathlon.

I connected with a close friend who was orthopedic surgeon at Mass General Hospital, trained at Harvard, and was a Marshall Scholar at U Chicago. Brilliant brilliant surgeon. He said that plica removal is a complete BS surgery and that it's a "non diagnosis". He sent me some literature showing me that the odds are improvement are basically no better than chance, and you're better off taking time off the aggravating sport and really focusing whatever muscle imbalance led to the injury in the first place. In my case, it was a weak posterior chain (weak glutes and hammies). I saw a great sports med doc (a non surgeon) and great PT who hit me hard with exercises to do at home. I'm finally racing again after 8 years on my ass and have never felt stronger. No knee pain whatsoever. Running and riding faster than ever.

Find a new doctor. I'd suggest a sports med doc. As the saying goes, a dog digs; a surgeon cuts.