From what everyone is saying on this, you'd think TLG is purposely trying to mislead us with these snapshots. (I'm not saying they aren't )
I've found a ball joint on this, another sign of possible steering. It's right where you'd think a ball joint would be on this
One of those knobs in the middle might actually be used for the steering, like previously suggested, because there should only be 3 knobs for the crane
One is on the crane (black 12t bevel gear)
One is on the base of the crane (tan 20t bevel gear)
One is the black 12t bevel gear on top of the black 2L axle extension
This leaves one remaining knob (black 2L axle extension), doesn't it?