He is expected to miss at least a month of golf while he recovers.

The surgery, announced on his website, came after Woods finished three shots behind Trevor Immelman in the Masters on Sunday.

He is likely to miss The Players Championship, but should return in time for the US Open at San Diego on June 12.

'I made the decision to deal with the pain and schedule the surgery for after the Masters,' he said.

'The upside is that I have been through this process before and know how to handle it. I look forward to working through the rehabilitation process and getting back to action as quickly as I can.'

The surgery was performed in Park City, Utah, by Thomas Rosenberg, who also operated on Woods' left knee in December 2002. He also had surgery in 1994 on his left knee to remove a benign tumour.

Swing coach Hank Haney said he knew Woods' knee was bothering him, but was not aware of the surgery until the golfer called him.

'He's been having a lot of trouble,' Haney said. 'He doesn't talk about stuff like that. He doesn't want to use excuses, you know?

'I don't think it affected his play. It affected his practice a little bit. He hit 14 greens in regulation on Sunday. Hard to say it was the knee.'

Woods gave no indication his knee was bothering him the first three months of the season, when he won his first four tournaments to extend a winning streak that dated back to September.

Said Mark Steinberg, Woods' agent: 'Tiger has been experiencing pain in his knee since the middle of last year. When he had it looked at by his doctors, arthroscopic surgery was recommended ... Tiger knew it would be better to have the procedure done as early as possible.'

The recovery is expected to take four to six weeks, meaning Woods will not be able to defend his title on May 1 in the Wachovia Championship.

Assuming the recovery goes as planned, he probably will return at the Memorial two weeks before the US Open.

ASSOCIATED PRESS