After upgrading a MySQL slave from 5.5 to 5.6.14 I attempted to execute the following query…

SELECT * FROM performance_schema.threads;

Despite the error log not reporting any issues I received the following error…

Native table 'performance_schema'.'threads' has the wrong structure

This was simply resolved by executing…

mysql_upgrade -h localhost -u root -p;

and then restarting the MySQL instance.