The Bavarians have revealed that the Spain international has suffered a suspected partial ligament tear in Saturday's 3-3 draw with Hoffenheim.
The Spain international was forced off just 25 minutes into Saturday's Bundesliga clash with Hoffenheim, and the Bavarians have now confirmed that the former Barcelona starlet is facing a spell on the sidelines.
"Thiago Alcantara has a suspected partial ligament tear in his knee," read a statement on Bayern's official Twitter feed. "Get will soon!"
It was a disappointing day for Bayern as they saw their 19-game winning streak in the Bundesliga come to an end, with Hoffenheim earning a 3-3 draw at the Allianz Arena.
However, coach Pep Guardiola rested a number of key players ahead of Tuesday's last eight first leg clash with United at Old Trafford.