This is where an indoor trainer can help.

Usually I start guys with their heel on the pedal, knee locked out, at the bottom of the pedal extension (roughly aligned with the seat tube.) That gets us in the ballpark. Then its on to 3-5mm adjustments.

Make sure, while pedaling under load at about 80 rpm, that your knee velocity is constant. If the back of your knee is picking up speed in its vertical velocity and opening velocity nearing the bottom of the stroke, then you are losing control of it and also stretching.

Make sure you're not rocking your pelvis to reach, or unnaturally pointing your toes. Most male cyclists are not toe pointers, and a proper height will return you to an unremarkable pedaling motion.

You'd be surprised how many experienced cyclists have their saddles too high. I ride with a guy who is blindingly fast compared with the rest of us in the club. He's barely taller than me, but his saddle is so high that I can't even stretch to effectively pedal his bike. He complains a lot about pain behind his knee, and hamstring issues, and when he pedals he points and rocks a lot. I've told him to drop his saddle, but he won't since a "pro" fitter set up his bike like that for him.