Collison, who suffered the injury during the Thunders' 123-115 win over the Atlanta Hawks on Friday, is expected to miss his team's next five games.
Following the match against the Hawks, Collison was seen wearing a walking boot and using crutches.
"I don't feel good," Collison said after the game. "Usually I know whether I can play [on it] or not, and I knew I couldn't play after I rolled my ankle."
Collison's injury couldn't have come at a worse time for the Thunder as they are already without the services of forward Kevin Durant and center Serge Ibaka, who are both nursing possible season-ending injuries.
Collison has been averaging 4.1 points, 3.7 rebounds and 1.3 assists per game this season.