Ronaldo sustained two bad injuries to his right knee while playing for Inter Milan in 1999 and 2000 but recovered to help Brazil win the 2002 World Cup.

He went on to play for Real Madrid before joining AC Milan in January 2007.

"We're all very sad and worried about Ronaldo," said Milan coach Carlo Ancelotti. "I don't want to say his career is over because only time can put the word end to his career.

"His team mates left the stadium quickly to reach the hospital to check on his condition. Being close to him can help him cope at such a delicate moment of his career."

Milan president Silvio Berlusconi said he believed Ronaldo would be able to resume his career.

"He still has an extraordinary physique. I'm confident in some months time he can return to be the player we all know," Berlusconi told Rai television.

Ronaldo is the all-time leading scorer in World Cup finals with 15 goals in three tournaments.

【体坛英语资讯：No problems after Ronaldo operation - surgeon】相关文章：

★ 体坛资讯：Zhu unfazed by ZZ suspension

★ 体坛英语资讯：Yi debuts for Bucks in win

★ 娱乐英语资讯：Lindsay Lohan to be caught on tape

★ 体坛英语资讯：Xing Huina Redemption: Marathoner looks to US coach for second chance

★ 体坛英语资讯：Tyson Gay: The fastest sprinter in Osaka

★ 娱乐英语资讯：Hong Kongs Chow takes on Japanese cartoon

★ 体坛资讯：Chinese to dominate Thailand Open finals

★ 娱乐英语资讯：Brangelina grab dogs, hit benefit in NY

★ 娱乐英语资讯：Britney Spears wins more time with sons

★ 娱乐英语资讯：Miss Serbia, Kosovo bury politics