Sounds exactly the same as me. I was exactly the same as you at 4 weeks.
2 years, 3 months later. 6 different physios, 3 orthopaedic specialists, 2 x mri, 1 x ultrasound, 3 x bike fits, 1 x hyaluronic acid injection. Hundreds of hours of all manner of exercises. Still not right.
The best guess is low level chondromalacia in my instance, hence the injection. The underlying mechanism/cause, has still not been attributed to anything. I’ve done all the quad/vmo exercises going.
I was 7 hours a week, 4.4w/kg. I recon I’ve lost around 40w due to patchy training. Crit racing career over, no longer a fast guy in my club ( I barely ride with those guys at all now).
So, not a success story by any means. If I could offer any advice (although perhaps I’m the worst person to offer it), it would be to perhaps not expect a quick fix, keep a bit of 1hr z2 consistency so you have some sort of base to bounce back from when things improve. Icing the knee has helped me.
I’m currently investigating with my physio/fitter if cleats positioned further back (not true ‘midfoot’, but with speedplay extender plate pushed back 5-10mm further back than typically furthest back position). This was after riding in trainers on £5 flat pedals from amazon, and realising the pain is massively reduced, and observing where my foot is happiest/natural. This aligns with the fact I cant leg press at the gym deeper than 90 degrees (more knee over toe) without pain.
This is almost certainly addressing a symptom, not the cause, but I don’t really care anymore. I’m also considering giving acupuncture a whirl, because, why not!
Every knee is individual. I would suggest asking for a referral from you PT to an ortho if things aren’t improving after 8-12 weeks.
Good luck, I genuinely hope you improve.