The diagnosis was made after the player underwent an MRT scan in Hanover on Thursday morning. The nature of the injury means that Andreasen is likely to be out of action for several months.
Doubly bitter blow
The news for the Reds' coach Mirko Slomka, who had started the 29-year-old midfielder in nine of the club's eleven matches to date in all competitions this season. It is also desperately unfortunate for Andreasen himself, having just returned to full fitness and first team action after more than two years out of the game due to a chronic groin problem.
The 16-time Denmark international had struck up a promising partnership in the centre of midfield with Sergio Pinto, netting six goals in the process. He had also earned a rapid-fire recall to the national squad before this latest injury setback put a halt to that progress.