Knightley starred as Elizabeth Swann in three Pirates films between 2003 and 2007, later making a cameo in the 2017 sequel Dead Men Tell No Tales.
Knightley said that the success of Pirates coincided with her receiving poor reviews and an Oscar nomination for Pride & Prejudice, which she found confusing at age 21.
Orlando Bloom, who co-starred in Pirates, said he understood Knightley's perspective and has positive memories from his time in the films.
Producer Jerry Bruckheimer confirmed a Pirates of the Caribbean reboot is in development, but Johnny Depp will not be involved.