Problem with queries, chatbox

SELECT u.id, u.group_id, u.num_posts_chatbox, m.id AS m_id, m.poster_id, m.poster, m.poster_ip, m.poster_email, m.message, m.posted, g.g_id, g.g_title_chatbox FROM chatbox_msg AS m INNER JOIN users AS u ON u.id=m.poster_id INNER JOIN groups AS g ON g.g_id=u.group_id WHERE m.posted > 0 ORDER BY m.posted ASC LIMIT 0,50;

mysql> explain SELECT u.id, u.group_id, u.num_posts_chatbox, m.id AS m_id, m.poster_id, m.poster, m.poster_ip, m.poster_email, m.message, m.posted, g.g_id, g.g_title_chatbox FROM chatbox_msg AS m INNER JOIN users AS u ON u.id=m.poster_id INNER JOIN groups AS g ON g.g_id=u.group_id WHERE m.posted > 0 ORDER BY m.posted ASC LIMIT 0,50;
+----+-------------+-------+--------+------------------+---------+---------+----------------------------+------+-----------------------------+
| id | select_type | table | type   | possible_keys    | key     | key_len | ref                        | rows | Extra                       |
+----+-------------+-------+--------+------------------+---------+---------+----------------------------+------+-----------------------------+
|  1 | SIMPLE      | m     | ALL    | NULL             | NULL    | NULL    | NULL                       |  100 | Using where; Using filesort |
|  1 | SIMPLE      | u     | eq_ref | PRIMARY,group_id | PRIMARY | 4       | forum.m.poster_id          |    1 | Using where                 |
|  1 | SIMPLE      | g     | eq_ref | PRIMARY          | PRIMARY | 4       | forum.u.group_id           |    1 |                             |
+----+-------------+-------+--------+------------------+---------+---------+----------------------------+------+-----------------------------+
3 rows in set (0.00 sec