Ruiz (wrist) underwent right knee arthroscopic surgery Tuesday, Martin Gallegos of MLB.com reports.
A patella tendon debridement and a chondroplasty procedure were performed on the knee. Ruiz -- who had already been ruled out for the season with a left wrist strain -- will rehab this offseason in hopes of being ready in time for spring training. The 25-year-old played 29 games for the Athletics this season, producing a .652 OPS with two homers and five steals.