French veteran Ribery to undergo ankle surgery
Ribery, 36, had to be helped off the pitch after a clash with Lecce midfielder Panagiotis Tachtsidis on November 30.
"In order to solve the problem, a joint stabilisation surgical treatment has been proposed which will be performed in the next few hours," Fiorentina said.
"At the end of the procedure, the times for resuming competitive activity will be announced."
Some Italian media said the former Bayern Munich star will be sidelined for two months.
Fiorentina are on a run of four consecutive defeats and are struggling in 13th in the league, five points above the relegation zone.