Borussia Dortmund midfielder Sven Bender underwent surgery on his right knee on Friday and will be sidelined for four weeks, the Bundesliga club said.

Bender, capped seven times by Germany, suffered the injury during training and will miss at least the first of his club's games, at Leverkusen on January 31, once the winter break ends.

Dortmund have been plagued by injuries this season and went into the break second from bottom of the table with just 15 points, 30 behind leaders Bayern Munich.