[Aoife]

(I'm not one of the injury peeps, but…)

It sounds like it could be an imbalance and weak posterior chain. Usually quad dominance can give knee pain and often like you describe. So while you should definitely listen to someone like Julie who knows way the hell more than me… I'd wonder if better targeting and activating your hamstrings and glutes will fix your issue. Certainly, it won't hurt. So RDLs, glute bridges, birddogs, leg curls on the physioball… that kind of thing would help.

If you're doing lunges and you find it hurts more if you're leaning your torso forward rather than staying upright, it could be a clue that this is part of your problem. When doing squats, deads, lunges, etc work on using your glutes… your quads shouldn't be doing all the work of straightening your legs.

I actually find that when I start up after a long hiatus, I just don't do loaded squats, and start with posterior work precisely because I rather easily end up like this if I'm not careful.

But anyway, welcome to the land of posting and I'm sure someone else will be of much more help than I am.