query_vars.php

<?php
/**
 * If pretty permalinks are turned on, we need to make the following query string variables 
 * available to WP_Query to sort by highest rated posts
 */
function my_query_vars( $qvars ) {
    $qvars[] = 'orderby';
    $qvars[] = 'meta_key';
    $qvars[] = 'order';
    $qvars[] = 'ignore_sticky_posts';
    return $qvars;
}
add_filter( 'query_vars', 'my_query_vars' );