The midfield general has been struggling with the problem during the early stages of the season and has been forced out of the Hoops' past four games.
Brown underwent a scan in London on Monday and the results have shown that he is gutted that he will require surgery which could put him out until mid-December.
"I have been told I'm looking at up to 10 weeks out and I'm absolutely sick," he told the Daily Record.
"I'd been hoping for good news but I could tell when the doctor checked me that something wasn't right. I had a bad feeling in the pit of my stomach and my worse (sic) fears have been confirmed.
"It isn't the same problem I had with my ankle - it's a different ligament altogether, although it may have been caused by the stress the old injury was causing.
"I am devastated. I feel I can't catch a break at the moment after all the injury problems I had last season.
"The last thing I needed was another lay-off like this. All I want to do is be out there helping my club and country."