The Rossoneri have signed the Guinea international on a co-ownership deal, while the Italian defender's brief spell at San Siro has come to an end
The Rossoneri signed the Guinea international on a one-year loan deal at the start of the 2012-13 campaign, but they have now opted to sign the 25-year-old on a co-ownership deal after he impressed in the first half of the season.
Acerbi, meanwhile, joined the San Siro outfit in the summer transfer window from Chievo, with Genoa holding the other half of the 24-year-old's rights.
Nevertheless, he will now be fully owned by the Grifone after he failed to impress at Milan in the past six months.
Milan have already signed Cristian Zaccardo from Parma in a player-exchange deal involving Djamel Mesbah as they aim to strengthen their squad before the winter transfer window closes.