Normally, when you'ld open your mouth completely, your jaw moves your mouth in one straight line, like in 1.
In 2, that's me, i can't open or close my mouth completely, without my mouth moving crooked for a bit (therefore the crooked arrow in 2: that's the way my mouth moves when completely opening or closing^_o). It's not normal, but i haven't had any serious problems with it i just don't open my mouth completely that much. (just to show people that it twitches crooked for a moment :P)