I've been having some pain in my left knee now for a few weeks (about 3-4) and decided that it's time to see the doctor. I brought in my training log so I could refer to my workouts, weights, etc. for the past few weeks as well.
He's a sports doctor (which is good as it's not just your average Joe) and it looks like I've got Patello-Femoral Syndrome and need to lay off squats (sorta), leg presses, and lunges are a complete no-no.
It was interesting to go through my log with him, for it appears the real damage occurred when I started doing lunges, as I haven't done them in about 20 years. Granted my form was probably off, but my notes in my training log kinda confirm it.
What's interesting is he's got me on a physio plan that DOES do squats, but it's a certain variation of them and I can't use heavy heavy weights (obviously).
These squats you start off normal, then quickly drop like your legs have been cut out from under you. You drop to a 45 degree angle and hold for 1-2 seconds, go up normally (slowly) and repeat.
My deadlifts are still good, as are extensions and curls and calves.
Cardio is just brisk walking on the treadmill on an incline and the exercise bike (no stair climbers, etc.)
Takes about 6 weeks to get better, but man I was so worried he was going to say that I'd have to take a break from the gym for a while.