Diarra to undergo arthroscopic surgery
"After undergoing several tests following a training session, during which Mahamadou Diarra felt severe pain in his right knee, it has been decided that he will have arthroscopic surgery next Monday," the club said in a statement posted on its Internet site.
The operation will be carried out at Madrid's La Moraleja Hospital, it added.
Spanish sports daily Marca said Wednesday that the 27-year-old defensive midfielder could be sidelined for between two to six months.
The reigning Spanish champions have struggled this season, in part due to a steady stream of injuries suffered by key players, and currently lie in fourth place, six points behind leaders Barcelona.
The club on Thursday presented its new signing, Dutch international striker Klaas-Jan Huntelaar, seen as a replacement for Ruud van Nistelrooy, who is out until the end of the season after a knee operation.