Indianapolis, IN (Best E Casino) - Indianapolis Colts safety Bob Sanders, already expected to miss a month with a high ankle sprain, has undergone arthroscopic knee surgery.

Colts owner Jim Irsay announced on Friday that Sanders had undergone the surgery because recovery from the high ankle sprain would take longer than recovery from the surgery.

Sanders, a two-time Pro Bowl safety and the 2007 Associated Press Defensive Player of the Year, has 15 tackles, including 10 solo, in two games for the Colts this season. He sustained the ankle sprain in Indianapolis' Week 2 win over Minnesota, and is out an indefinite period of time.

The fifth-year safety out of Iowa has yet to play an entire 16-game season in his career. He played in 15 games last season, but only four in 2006 due to a knee injury.