The Brazil playmaker is likely to be out for 15 days while he recovers from the problem.

A statement posted on Milan's official website, www.acmilan.com, on Friday read: "Today Kaka underwent a check-up by professor Martens who had already checked up on him over the past few months.

"Professor Martens confirmed that the player's knee is inflamed, and advised him to continue for 15 days with the recovery programme he is following."