AC Milan have confirmed that full-back Andrea Conti will undergo an operation after sustaining another injury to his knee.

The 24-year-old ruptured his cruciate ligament in September, prompting the need to go under the knife in the same month, and had been hoping to recover in time for the derby against Inter Milan.

However, Conti injured the same knee in training last month and, despite initial hopes that the problem was just a sprain, the Rossoneri have now announced the need for another operation.

"Following Andrea Conti's left knee recent sprained trauma, AC Milan medical staff considered the clinical findings with professor Freddie Fu and professor Pier Paolo Mariani," Milan said in a statement.

"The unanimous diagnosis is that of a residual rotational instability of the operated knee that can be fixed through a new surgery that will be carried out tomorrow by professor Mariani at the Villa Stuart Clinic in Rome."

Conti joined Milan in July from Atalanta BC, but has made just two appearances for the Serie A giants.