The defender is set to go under the knife after tests showed a tear in his cartilage and is likely to miss games against Torino, Napoli and Celtic
De Sciglio, 20, has undergone tests which revealed a tear to the cartilage in his knee and could now be sidelined for up to two months.
The full-back is likely to miss the Rossoneri's clashes against Torino and Napoli in Serie A and the Champions League Group H opener against Celtic.
The Italy international has endured an injury-interrupted start to the campaign having played just once - against PSV in the second leg of the Champions League play-off - and will undergo surgery in Milan.
Meanwhile, Milan's other full-back Ignazio Abate, who picked up a muscle strain on international duty with Italy, will undergo further tests in eight to 10 days' time to see the extent of his damage.