Veteran Adelaide ruckman Sam Jacobs has undergone knee surgery and will miss the next six weeks of the season.

The 31-year-old hasn't played since hurting his right knee against Sydney in round two.

Jacobs had surgery on Wednesday to fix a meniscal problem and faces a four-to-six-week rehabilitation program, the Crows say.

"We expect Sam to progress quickly through the next four-six weeks of rehab and be back to his best," Adelaide's medico Steve Saunders said in a statement.

The Crows will be forced to rely on novice Reilly O'Brien to lead their rucks in the absence of 198-gamer Jacobs, who has been a mainstay in Adelaide's line-up since crossing from Carlton at the end of 2010.

AAP