Leicester City boss Brendan Rodgers confirmed on Wednesday that Barnes – who has not played since a 3-1 home loss to Arsenal on February 28 – underwent a second operation to clean out the knee.
The procedure means the Foxes will have to do without the 23-year-old for the Premier League run-in, as well as the FA Cup final against Chelsea on May 15.
Barnes scored nine goals and provided four assists in 25 league games for Leicester, who are on course to qualify for next season's Champions League with a top-four finish.
"We've had a slight setback with Harvey," Rodgers told the media.
"He's just gone in to have a second, minor operation, just to clear up some of the damage in his knee.
"It will probably rule him out for the rest of the season."