By what mechanism does the mandible autorotate along with the maxilla?

[KronosAlphason]

Both of my jaw are recessed and have grown too much in a downward direction. I will probably either have double jaw surgery, with advancement of both the maxilla and the mandible, or upper jaw surgery.

I have read in a lot of places that the lower jaw will automatically rotate to meet the new position of the maxilla. In my case, my maxilla will most likely be moved forward and up, and according to these prediction, the mandible will rotate to meet the new maxillary position and the gonial angle will be less steep.

I am wondering how the body can perform this? How does it know where the teeth are in this new position? What is the mechanism behind the autorotation?

Hope you have the answers 

[PloskoPlus]

The elastics you'll wear after surgery will train the jaw muscles for the new position.

[Tiny]

the gonial angle will be less steep.

Not quite.  The occlusional plane will be less steep.  The actual bony structure of the gonial angle will be the same.  The only procedure that can change this is IVRO (inverted L) or it can be camouflaged with implants.