The Bristol City defender was on the receiving end of a dangerous lunge during his side's Championship fixture against Peterborough United and will miss forthcoming games
The former Manchester City player was on the receiving end of a challenge from Tyrone Barnett which resulted in his being stretchered off with 15 minutes remaining in the game and the Robins' boss Derek McInnes was furious in the aftermath of the game.
"(Greg) Cunningham has got severe ligament damage," he told the club's official website. "It's too early to say how long he'll be out but he certainly won't be with us for a few weeks."
Cunningham recently joined Bristol City from Premier League champions Manchester City and had played in all six of the club's league fixtures this season.