what happened to the joker after the dark knight

After the events of The Dark Knight, the Joker was arrested and left for the police to come collect him. However, he was not mentioned in the third film of the trilogy, The Dark Knight Rises, as director Christopher Nolan promised not to recast or address the Joker in the film after Heath Ledgers death. The official novelization of The Dark Knight Rises suggests that the Joker was the sole inmate at Arkham Asylum. However, there is no clear in-universe explanation for his absence in the film. There were plans to include the Joker in The Dark Knight Rises, but Ledger's death changed the course of the movies.