The procedure was performed Thursday morning. Orton is not expected to begin practicing again until at least February.
The 6-foot-10, 255-pound center was the 29th overall pick in the NBA draft after playing only one season at Kentucky. Orton missed all of training camp with knee injuries, which have plagued him since high school.
Then he was assigned to the Magic's NBA Development League affiliate in New Mexico, but he reinjured the knee in his second game.
Orton wrote on Twitter that the doctor told him the surgery went "better than he expected." Orton is a long-term project for the Magic and wasn't expected to see much playing time this season.