Mane, 30, picked up the injury in Bayern's 6-1 win over Werder Bremen on Nov. 8. He was substituted on 20 minutes with the team describing it the day after the match as an injury to the head of the fibula bone in his lower right leg.
However, the team revealed in a news conference on Thursday that further scans on the two-time African player of the year showed he would require surgery for the injury and would not be able to play in Qatar.
"The latest news has arrived just now, and since the injury to Sadio Mane which happened on Nov. 8, we made contact very quickly with Bayern Munich to have the information," Senegal team doctor Manuel Afonso told reporters. "The next day, the club communicated to us the images of the first MRI he undertook, which showed an injury to his right knee and for which we went to examine the player and take another look at the images right at the heart of the club.
"This is why I travelled on the 10th and 11th of November to get all of his data. It was decided to undergo another MRI today [Nov. 17] to understand the evolution and determine whether or not it was possible for Sadio Mane to keep his place at the World Cup.
"And, sadly, today's MRI has shown that the evolution is not as favourable as we'd have imagined, and so we've resolved -- sadly -- to declare that Mane is forfeit for this World Cup, and normally a surgical intervention will be scheduled very shortly."
Bayern confirmed later on Thursday that Mane's surgery was successful and he would soon return to Munich.
"Sadio Mane underwent successful surgery in Innsbruck by Prof Christian Fink and Dr Andy Williams from London on Thursday evening," their statement read.
"During the operation, a tendon was reattached to the head of his right fibula. The FC Bayern forward will therefore no longer be available to play for Senegal at the World Cup and will begin his rehab in Munich in the next few days."