What confuses me about vibrato

I simply cannot grasp how one moves the hand — requiring some muscle tension, obviously — and manages to press down the fingertip to the fingerboard, and simultaneously keep the first knuckle loose enough to rock back and forth.

How does one transfer weight into the tip of the finger without passing that weight through the first knuckle? You can’t have a hinged board and press down on one side, and have that pressure translate through to the other side without it passing through the hinge as well. You can’t transfer pressure through a hinged board and keep the hinge loose enough to wobble at the same time.

I simply don’t get it. Now, I’m nowhere near where I need to be to start worrying about this and given my track record of loveloveloveGET!IT!AWAY!, I imagine it will be um … a while … before I’m ready to even care about it. But I just cannot think through how this works. And I know that until I can wrap my brain around it, it’s even less likely to happen.