Leicester targeted the 28-year-old as a replacement for Danny Drinkwater, who was sold to Chelsea for £35m in the final hours of the summer transfer window.
Drinkwater was announced as a Stamford Bridge arrival at 1.30am on September 1 but because Silva was an international transfer, Leicester had to await clearance to announce the deal.
Sporting said at the time in a statement: “Sporting Club de Portugal… informs the market that we have reached an agreement with Leicester for the definitive transfer of the sporting and economic rights of the professional soccer player Adrien Silva. The registration of the same (player) is awaiting confirmation of FIFA.”
Silva is a product of Sporting’s academy and has had loan spells at Maccabi Haifa and Academica. He has earned 20 caps for Portugal, despite being born in France.
He is a Euro 2016 winner with Portugal and has scored 32 goals in 136 league appearances during his six years with Sporting.