Badstuber tore his cruciate ligaments last December in Bayern's 1-1 draw with Dortmund.
After a first operation, complications necessitated surgery for the second time before a third surgery after he suffered a relapse on his road to recovery.
Now, he has been told that a further operation will be required once his wounds are healed again.
"Until that happens, it could be between three or six months," the 24-year-old, who risks not only missing the entire 2013/14 season, but also next summer's World Cup, told Sport Bild magazine.
"I just hope it is closer to three or four months since I used some of my own cartilage in the operation."
Tissue from Badstuber's left knee will be inserted in his right knee in the operation which will be carried out in the United States as soon as the structure of his operated knee is strong enough for further surgery.
The earliest date for that is October, and with a six-month recovery period to follow, he is almost certain to be out of action for the entire season, if not longer.