The 25-year-old suffered the injury during training ahead of his country's friendly with Scotland on Wednesday and, after consulting with the Poland national team doctor, Lewandowski has opted to return to Westphalia to undergo further tests.
'I shouldn't play'
"I have a slight strain of the cruciate ligament. The doctor says I shouldn't play on Sunday," Lewandowski told Bild on Tuesday. BVB club doctor Markus Braun will determine the full extent of the striker's injury on Wednesday, but it is unclear whether he will be fit to face SC Freiburg in the Bundesliga this weekend.
Dortmund coach Jürgen Klopp is currently without four first-team regulars, with Neven Subotic, Jakub Blaszczykowski, Sven Bender and Ilkay Gündogan all sidelined with long-term injuries.