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 fullback 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 playoff - and will undergo surgery in Milan.
Meanwhile, Milan's other fullback, 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.