Ricketts ruled out for rest of season
Ricketts, 29, sustained the injury in the FA Cup fourth round replay win over Premier League rivals Wigan Athletic on Wednesday.
He will miss Wales's Euro 2012 qualifying clash with England in Group G on March 26 and is set to undergo surgery on Friday.
"The likelihood is that he will be missing for about six months, which is a big blow for Sam first and foremost," Bolton manager Owen Coyle told the club's website.
"He has been outstanding for us... and we wish him a speedy recovery.
"It was very innocuous in terms that he sustained the injury by tracking the winger. He has put his foot down and stumbled so it is very unfortunate. With the speed that the game is now played then these type of injuries can occur."
Bolton are enjoying a fine season in the Premier League, sitting in eighth place.