20 Fashion icons that have left their mark in cinema no thoughts, just keira knightley in that green dress in atonement Anyone else still thinking about Keira Knightley's backless green dress from Atonement, 13 years later? At the link in bio, our style editor examines why the backless trend became an unlikely Keira Knightley's green dress from Atonement we still talk about you Netflix Facebook Keira Knightley Editorial Stock Photo Stock Image Shutterstock Editorial Keira Knightley V neck Backless Green Dress Spaghetti Straps Prom Dres Hoprom