Having had knee pain most of my adult life (even predating an MCL strain, unrepaired ACL, and recent meniscus and cartilage removal surgery) I love you are thinking this way. Getting stronger is the long term answer (arthritis aside - I somehow have escaped that one).
A good PT is a great place to start. A good one, in my non credentialed opinion, is one that will focus on progressive strength training (vs primarily focused on constant and endless stretching). I have seen a few different PTs and gotten materials from across the interwebs to formulate what I think is right for me. It's worked well enough that my post surgery PT and Dr appointments were 5 minutes - I was beyond the (low) bar of measurement they use to "return to normal activities".
My daily routine to build my strength back up is lunges, RDLs (not a fan of straight deadlifts at 40+), box touchdowns, and calf raises. I'm slowly ramping up from body weight to added weight before resuming gym weightlifting (leg extensions, ham curls, squats, leg press, bulgarian squats, etc.)
Again, that's what's worked for me but my universal advice is to find what works for you, go slow, and drop all ego to focus on good form.
Good luck.