Attaching stair newel posts are not always as straight forward as we would like. Different design constraints require that installers get a little creative when they attach the newels.  After they have been installed there is always the possibility that after years of use newels will become somewhat shaky.  This Old House has a brief article on reinforcing your stair newel that you may find useful if you have a wobbly newel on your stairs or outside deck. You can read it here: Reinforcing Wobbly Newels

Newel Post