Djourou, who has made 144 appearances for Arsenal since 2004 without ever becoming an established first-teamer, will move to the Bundesliga side for the remainder of the season.
He is the second Arsenal player to go out on loan since the opening of the transfer window following striker Marouane Chamakh's move across London to West Ham United.
Djourou has not played in the Premier League for Arsenal this season, his two appearances coming in the League Cup.
Get the best features, fun and footballing frolics straight to your inbox every week.
Thank you for signing up to Four Four Two. You will receive a verification email shortly.
There was a problem. Please refresh the page and try again.