On Monday, Dr. Eaton repaired the torn medial meniscus in Iwamura's knee and also determined that the second baseman had suffered only a partial tear of his anterior cruciate ligament.
Because Iwamura had just a partial tear, Eaton was able to use arthroscopic surgery rather than reconstruction surgery, which was the original diagnosis.
Iwamura's injury had been considered season-ending, but now the Rays are reporting that Iwamura could return to game activity in six to eight weeks.
The surgery was performed at St. Anthony's Carillon Surgery Center in St. Petersburg.
Iwamura was hitting .310 after 44 games this season, which is his third since coming to the Rays from Japan.
Bill Chastain is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.