Mysql is not using index on query - mysql

Question

here is my explain result.
+----+-------------+----------------+--------+-------------------------------------------------------+-------------+---------+-------------------------------------+------+----------------------------------------------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+----------------+--------+-------------------------------------------------------+-------------+---------+-------------------------------------+------+----------------------------------------------------+
| 1 | SIMPLE | client_address | ALL | client_id | NULL | NULL | NULL | 1619 | Using where; Using temporary; Using filesort |
| 1 | SIMPLE | clients | eq_ref | PRIMARY,contract_id,contract_id_2 | PRIMARY | 3 | defenselaw.client_address.client_id | 1 | Using where |
| 1 | SIMPLE | user_infos | eq_ref | user_id | user_id | 3 | defenselaw.clients.client_rep_id | 1 | Using where |
| 1 | SIMPLE | users | eq_ref | PRIMARY | PRIMARY | 2 | defenselaw.user_infos.user_id | 1 | Using where; Using index |
| 1 | SIMPLE | contracts | eq_ref | PRIMARY | PRIMARY | 3 | defenselaw.clients.contract_id | 1 | NULL |
| 1 | SIMPLE | documents | eq_ref | contract_id,contract_id_2,contract_id_3,contract_id_4 | contract_id | 3 | defenselaw.clients.contract_id | 1 | Using where |
| 1 | SIMPLE | client_info | ref | client_id,client_id_2,client_id_3,index5 | client_id | 3 | defenselaw.client_address.client_id | 1 | Using where |
| 1 | SIMPLE | location | ALL | PRIMARY | NULL | NULL | NULL | 1 | Using where; Using join buffer (Block Nested Loop) |
+----+-------------+----------------+--------+-------------------------------------------------------+-------------+---------+-------------------------------------+------+----------------------------------------------------+
here is the query.
SELECT
contracts.contract_id,
documents.documentKey,
documents.document_name,
documents.notify_accountant,
clients.client_first_name,
clients.client_middle_name,
clients.client_last_name,
clients.client_rep_id,
client_address.client_street,
client_address.client_apartment,
client_address.client_city,
client_address.client_state,
client_address.client_zip,
client_info.client_email,
client_info.client_home_phone,
client_info.client_work_phone,
client_info.client_cell_phone,
client_info.client_fax_number,
contracts.contract_agreement_date,
user_infos.user_first_name,
user_infos.user_last_name,
location.location
FROM
`contracts`
LEFT JOIN
`clients`
ON clients.contract_id = contracts.contract_id
INNER JOIN
`client_address`
ON client_address.client_id = clients.client_id
INNER JOIN
`client_info`
ON client_info.client_id = client_address.client_id
LEFT JOIN
`documents`
ON contracts.contract_id = documents.contract_id
LEFT JOIN
`user_infos`
ON user_infos.user_id = clients.client_rep_id
LEFT JOIN
`users` ON
users.user_id = user_infos.user_id
LEFT JOIN
`location`
ON location.location_id = user_infos.location_id
WHERE client_info.client_role = 'primary'
AND documents.archive = 0
ORDER BY
documents.created_on DESC
Could someone explain to me why my index on client_address isn't being used? I am lost here as I just don't know what to do. It's not that complicated of a query its just rather large. Yes, stackoverflow, I understand the post is mostly code. What more do you want from me? How much more can I say about this other than my query isn't using an index and its causing a really slow query here.
+----------------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
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| client_address | CREATE TABLE `client_address` (
`client_address_id` mediumint(12) NOT NULL AUTO_INCREMENT,
`client_id` mediumint(12) NOT NULL,
`client_street` varchar(40) COLLATE utf8_bin NOT NULL,
`client_apartment` varchar(20) COLLATE utf8_bin NOT NULL,
`client_city` varchar(80) COLLATE utf8_bin NOT NULL,
`client_state` varchar(80) COLLATE utf8_bin NOT NULL,
`client_zip` varchar(80) COLLATE utf8_bin NOT NULL,
PRIMARY KEY (`client_address_id`),
KEY `client_id` (`client_id`)
) ENGINE=InnoDB AUTO_INCREMENT=2167 DEFAULT CHARSET=utf8 COLLATE=utf8_bin |
+----------------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
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