Dr. Neal ElAttrache performed the surgery, which was a 35-minute arthroscopic procedure to clean up the wear and tear behind the kneecap.
Ethier's rehab will take six to eight weeks and will start within the next week.
An All-Star this season, Ethier's numbers began to decline after the break, and he played his last game on Sept. 6. He finished the season hitting .292 with 11 home runs, his lowest total since 2006.
"No complications once they got in there," manager Don Mattingly said. "They didn't have to do anything that would have had to push the rehab into a longer period of time. So that went really well."