Manager Mick McCarthy has confirmed that the 28-year-old midfielder is set for a spell on the sidelines after picking up the injury against Blackpool on Saturday.
"Karl is out for two months with medial knee ligament damage," McCarthy said.
"He's had a scan and I think there's a slight tear. It's a huge blow, especially with Dave Edwards out with a thigh strain.
"Karl's been great and he's been an ever-present unless he's been injured - and the injuries he's had have been serious, with his knee and damaged spleen. It's a big loss."
Source: PA
Source: PA