The Republic of Ireland international was scheduled to remain with the Championship club until the end of the season, but has now returned to Eastlands after a successful operation.
Cunningham left Leicester with praise ringing in his ears from manager Sven-Goran Eriksson, who would like to see the 19-year-old back at the Walkers Stadium.
"He has been brilliant for us and one of our best players all season. He is very brave, has a good left foot and is a good player," said Eriksson.
"He will be away for at least four months. It is really bad luck. We don't know if we will have him back before the end of the season and I don't think anyone could say about that at this stage."
Eriksson has said he would like to sign Cunningham on a permanent deal, but the left-back only signed a new four-year deal at Manchester City in August.
Source: PA
Source: PA