脊

Pictogram of the spine (backbone); two 二 characters are the shoulder-blades or ribs. 人 character is like an arrow pointing up to show the spine going up the back. 月 character is the two legs and two vertebrae. It’s a stylized picture of the human bones from the back.

二 人 二
  月

   s
   P
  JI
SPINE
   E

Gee! J.oInts I.n SPiNE!