Try this ...
if you want users to type
yourdomain.com/wiki/SomeArticle
to get
yourdomain.com/rootdirectory/index.php?title=SomeArticle
use
RewriteRule ^wiki/(.*)$ rootdirectory/index.php?title=$1 [QSA]
then go into your localsettings.php and set
$wgArticlePath = "/wiki/$1";
Note: This will only make pretty urls for article pages - not for
edit pages.
Hope this works for you
It's been a while since i've messed around with this
but i experienced the same frustration when i first tried to get
pretty urls