In a statement, the Bundesliga club said that Gnabry will be out for "an extended period".
The reigning German league champions have not given an exact timeframe for his return, but according to German media, Gnabry has played his last club match of the season and is therefore at risk of missing this summer's World Cup in North America.
Gnabry started all six of Germany's matches in World Cup qualifying and scored three goals.
