how about not guessing and get an MRI..is that an option?
You said your not exactly young anymore yet ppl are thinking tedonitis..well odds are its a bare minimum of tenoNOSIS which can subject to future injury easily.
Maybe there is already a partial tear...maybe you have partial avulsion..possible hoffa fat pad all sorts of inflammed..
Ohh..how about about its not really patellar but its chondral..maybe fem trochlear cartilage is all messed up..or a plica is rubbing.. how about a joint body sitting there.
I can go on and on and on all day.. see a doctor. Get an exam. Get an mri.. find out what is wrong and treat what the underlying issue actually is.
Its like saying..ohh my car makes a weird sound from the engine when i hit the gas....instead of finding out what is wrong someone says oh my car made a weird sound once and it was an exhaust lead from my headers..sooo you should tighten them up... anyone anywhere would be like wtf... but when it comes to medicine we are gonna start injecting stuff and taking things without even knowing the issue.
Get worked up. come back. PM me after you post the MRI findings and we can discuss management.
How would it help to know what specific pathology is causing the pain? It's not like there are many specialized (non-surgical) treatment options. I get that an MRI is helpful when considering surgical options, and if his knee pain does not improve, that is definitely something to be considered.
The alternative to surgery is to allow your own body to repair the damage, and to prevent excessive inflammation from doing additional damage.
A treatment plan as above is a shotgun approach that would help irrespective of whether the problem is tendinopathy, chondral, or whatever. Excess inflammation is adressed with Curcumin, cold packs, NSAID, and GH and BPC157 have been shown to promote healing in joints, tendons, ligaments alike, so again you may not need to figure out the exact pathology to treat it.
Also, given that both knees are affected and that the pain was preceded by high intensity weight training, a tendinopathy seems very likely.
And lastly, even if it is a structural issue that can't be addressed with the above approach: as long as training is restricted to pain free movements, you won't make the damage worse. So if the problem persists, you can still get an MRI and go for surgery.