AC Milan have confirmed Riccardo Montolivo has undergone surgery on his torn anterior cruciate ligament.

Montolivo sustained the injury while on international duty in the 1-1 draw with Spain on Thursday.

The Milan statement confirms the midfielder is expected to be out of action for five to six months, save for complications.

It is the second serious injury Montolivo picked up while playing for Italy, as he fractured his leg in a friendly against the Republic of Ireland in May 2014.