Dustin Johnson has knee surgery

Dustin Johnson underwent right knee surgery Tuesday and will miss all golf tournaments until 2012.

Johnson had arthroscopic surgery to repair damaged cartilage and should be ready to compete again by mid-January. He apologized to several fans on Twitter who asked if he would be playing events in December.

"Looking more and more like I'll be back on the horse in early January," he responded to one of them.

According to a story on the PGA Tour's website, the injury has bothered Johnson since July. He last played in the Presidents Cup in Australia two weeks ago.

Johnson was initially expected to defend his title at the Shark Shootout next week. He had one victory this year, at The Barclays, and is a five-time PGA Tour champion, He has exempt status through 2014 for his Barclays victory.