The operation was performed by Dr. Bernard Bach on Tuesday in Chicago. The Blues say there is no timetable for Fabbri's return.
The 21-year-old Fabbri has 29 goals and 37 assists in 123 career games with St. Louis. He was selected by the Blues in the first round of the 2014 draft.
Fabbri missed the final part of last season after he tore the anterior cruciate ligament in his left knee on Feb. 4. He had surgery and was cleared to play on July 31, but he re-injured his knee during training camp.
St. Louis began the day on top of the Central Division with an 11-3-1 record.