Neutral zone is not the same as loose packed position of a joint.
It is as described 2 posts above; ROM that a joint can do without tightening passive structures. Neutral zone is most commonly used about the back in question of stabililty problems. I'm not very good at explaining, but read further here:
Panjabi:
www.ncbi.nlm.nih.gov/entr...t=Abstract
and this can be of value:
dianelee.ca/published/mas...Thorax.doc
gotta go...
/øystein, Norway.