Early in The Dark Knight Rises, Bruce is seen limping with a cane. Some characters allude to an injury sustained from a fight, but we never see this in The Dark Knight. At the conclusion of that film, we see Batman surviving his run-in with Harvey Dent and escaping while running away.
What happened to Bruce Wayne/Batman's knee in between The Dark Knight and The Dark Knight Rises?
Note: we know the injury is real because we see Bruce requiring a knee brace of some kind prior to him suiting up as Batman.