Ronaldo out with knee injury.

Real Madrid striker Ronaldo will reportedly be sidelined for a month following an injury to his left knee.

Ronaldo, who has struggled to make the starting lineup this season, was hurt in Thursday's 5-1 Copa del Rey win against third-division Ecija.

The Brazil striker scored his first gal for Madrid since April 8 in the 68th minute after several earlier misses.

Sports daily Marca said on its Web site that Ronaldo had a ligament injury to his left knee.

Newspaper El Mundo said Ronaldo sustained the injury while shooting at goal and could be out for the rest of this year. (AP).