Knee clunking at bottom of pedal stroke

Sort of a soft thudding, internal thing. Does not hurt.
Maybe on the front side. Rather like snapping the knee when you bend the leg and straighten it, but not so sharp a snap.
Not fully pushing down or bottoming out on that leg lessens it or makes it disappear, lowering the seat has made it disappear.
But, lowering the seat makes my other knee flare out some. Seems to be no height that makes both legs happy.
Knee sometimes feels full starting a couple hrs after the ride.
Rode this a.m. It felt full all afernoon and continues.

Standing with feet close together and lined up in order to touch toes this eve I was looking down and noticed the right knee appeared more forward than the left. The legs were straight. This is a new one on me.

I know… go see an expert. Meanwhile, anyone have any similar experience or thoughts?