The Argentinean midfielder sustained the injury during his side's 1-1 draw with Hamburg in the Bundesliga.

The news will come as a blow to Sosa who has just returned to Bayern's squad after recovering from a back injury.

Bayern coach Ottmar Hitzfeld will face selection headache as he has already lost attacking duo Luca Toni and Miroslav Klose because of injury.

Sosa has joined the Bavarian club from Argentina's Estudiantes in the close season for nine million euros ($12.2 million).