
The defender strained ligaments in his left knee while training with the Germany squad in Cologne on Thursday.
Lahm has pulled out of Saturday's Euro 2008 qualifier against Wales in Cardiff, and will miss Germany's friendly at home to Romania on Wednesday.
He will also be out of Bayern's Bundesliga meeting with Schalke 04 the following Saturday and the UEFA Cup match against Portuguese side Belenenses on September 20, the club said.
Meanwhile Werder Bremen midfielders Torsten Frings and Tim Borowski are making progress as they attempt to recover from injury, Werder co-trainer Wolfgang Rolff said Friday.
Both are taking part in individual training programmes at the club's training ground, although it remained unclear when they would be able to take put in full training.
Frings has suffered cruciate ligament damage while Borowski is out with a knee ligament injury.
DPA