Paul George injures knee in second NBA pre-season game with 76ers
George was guarding Atlanta's Jalen Johnson in the first half when he appeared to plant his leg awkwardly.
He played no further part after having scored eight points on three-of-five shooting with two rebounds, one assist and one steal in just over 12 minutes on court.
George told the Philadelphia Inquirer that he felt the hyper-extension and knew he needed to have the knee examined but added "I'm not too concerned about it."
Sixers coach Nick Nurse said he was hopeful George would be back in action "right away".
George's injury comes a day after Philadelphia announced that star big man Joel Embiid wouldn't play in any pre-season games as part of the management plan for his surgically repaired left knee.
Embiid played in just 39 games last season because of a torn lateral meniscus, returning after surgery with seven games left in the regular season.
He was still wearing a knee brace when he helped the United States win gold at the Paris Olympics.
Asked Monday if there were concerns about Embiid's availability for the 76ers' season-opener against Milwaukee on October 23rd, Nurse said he was "not really sure where we're at with that".
"But we are right on course with the plan that we kind of set out," Nurse added.