The Daily Mail says the 30-year-old was advised by his specialist last week that more surgery was required.
Ritchie underwent the operation on Tuesday and will have to wait until January before stepping up his bid for a return to action.
The Scot suffered the injury in a challenge with Leicester's Hamza Choudhury during Newcastle's League Cup exit.
He was operated on in October only to suffer a setback in training and Bruce said after Monday night's 2-0 defeat at Aston Villa that the player needed a period of rest. Ritchie was in surgery the following day and will not be available for the next eight games at least.