The news was revealed in an interview with the Australian Daily Telegraph on Friday morning.
The report also states that Whittaker is “likely” to be sidelined until 2018 to overcome an array of “niggling injuries,” but the newly crowned champion did not give a specific time frame when asked.
Whittaker claimed that the injury is considered “serious” and that it “hurt like hell” when it happened in the opening round of his bout with Romero.
“Doctors always think the end of the world, right? If it was up to them I’d be in a wheelchair,” he told the Daily Telegraph.
“But I’m extremely lucky to have a great sports doc in Andrew McDonald. He works with South Sydney (as head of medical) so he’s seen a lot of sports injuries and knows his athletes well.
“The injury itself, it’s not really my job to understand. All I can say is that it’s a serious grade two medial ... and hurt like hell when it happened.”
With Romero now courting a date with UFC middleweight champion Michael Bisping despite his loss to Whittaker, the 26-year-old insisted that he would not be worried if Bisping looked to fight someone else while his injuries heal up.
“No, not at all,’’ he said. “I’ve never worried about what other fighters do and that’s served me well in the past.”
In the interview, Whittaker also revealed that he suffered a "strain" on the same knee four weeks out from UFC 213, but thought he would be in good enough condition to compete on it.