The 29-year-old suffered the injury in a clash with Jay McEveley in the 1-0 win over Derby on Saturday.
Edwards, who was playing in only his third game since coming back from a hamstring tear, left the Stadium of Light on crutches on Saturday.
"The good thing is that it's a clean break with no other complications," confirmed his agent Mike Berry.
It is the latest in a string of injuries that the Trinidad & Tobago international has suffered since his £1.4m switch from Luton in January.
that sums it up right dey[/i]
"It has been a nightmare for him. He got over the hamstring injury and came back against Everton and then got injured again versus Derby."
Edwards returned to action in the 1-1 draw with local rivals Newcastle in November, almost three months after damaging his hamstring at Birmingham during the opening week of the season.
The news will come as a bitter blow to Black Cats manager Roy Keane, who finds his options down the right limited in both midfield and defence.
Keane has admitted fitness concerns have exposed the lack of depth in his squad, and said that he will hope to address the situation when the January transfer window opens.
