Guard Tony Allen, one of the Celtics' three first-round picks in 2004, underwent successful arthroscopic right knee surgery Wednesday to repair torn knee cartilage.

The surgery was performed by Dr. Brian McKeon at New England Baptist Hospital, and Allen is expected to begin rehabilitation immediately under the medical staff's supervision.

The 6-4 Allen, who was Boston's third first-round pick (25th overall) in 2004 behind Al Jefferson and Delonte West, averaged 6.4 points and 2.9 rebounds in 77 games last season. The Celtics went 21-13 in his 34 starts.

Allen, who scored a team-high 17 points in the Rookie Challenge at All-Star Weekend last season, averaged 16.8 points on 55.9 percent shooting during the 2005 Reebok Vegas Summer League.