The striker had a history of knee problems, with two separate injuries to his right knee while playing for Inter (1997-2002). He battled back both times and recovered in time to help Brazil win the 2002 World Cup and claim his third FIFA World Player of the Year award. In January 2007, he joined Milan after five seasons with Real Madrid. On 13 February 2008, he injured his left knee while leaping for a cross in a 1-1 draw with Livorno. The injury ended his season and there was speculation that it would end his career as well.
Ronaldo, however, was determined to return. He returned to Brazil and started training with Flamengo to rehabilitate his knee. The Rio club indicated their willingness to sign him once he was able to play, but, in December 2009, he controversially signed instead with their league rivals Corinthians.
On 4 March 2009, he made his first appearance for Corinthians, coming on as a substitute in Copa do Brasil match against Itumbiara. In the match against Palmeiras on 8 March, he again entered as a substitute, coming on in the 63rd minute with his side down 1-0. He quickly made his presence felt, sending a booming strike off the crossbar in the 78th minute, before heading in the equalizing goal in the 93rd minute. He ran behind the goal to celebrate with the Corinthians supporters, causing a mild pitch invasion.
Ronaldo finished the season with 10 goals in 14 matches and recently signed an extension to remain at Corinthians through 2011.