Simon Kjaer is expected to be out for months after AC Milan announced on Thursday the Denmark centre-back had damaged ligaments is in left knee.

Kjaer was stretchered off early on in Milan's 3-0 win at Genoa on Wednesday and the Serie A giants revealed in a statement he would be going under the knife to repair the damage on Friday.

"The MRI and specialist evaluation Simon Kjaer underwent this morning confirmed the need for an arthroscopy on his left knee to repair ligament damage," said Milan.

"Surgery is scheduled to be performed tomorrow."

The 32-year-old joins a growing list of absentees for Stefano Pioli's side, with Olivier Giroud, Ante Rebic and Davide Calabria among those unavailable.

Kjaer is one of Milan's most senior players and will be a huge miss for Pioli as his team prepares for some key fixtures.

Milan take on Salernitana at the San Siro on Saturday before hosting Liverpool three days later as the Rossoneri bid to make the last 16 of the Champions League.

They then have the visit of Serie A leaders Napoli coming up on December 19 as a tight title race heats up.

Milan sit second in Italy's top flight, just one point behind leaders Napoli who could only draw 2-2 at Sassuolo while the seven-time European champions thrashed Genoa.