I did not "stage door" to meet Keira Knightley when I saw Therese Raquin, but I was quite nearby when she came out.
She came out rather quickly after the show... under 10 minutes, I would say. It was a brisk night, and it is heavily a subscription audience, so the crowds were not excessive. She did take the time to sign all Playbills, at least from what I could observe, but she had theatre security along side her and they did announce that she would not be posing for pictures.