Irving was helped off the floor in the third quarter after falling awkwardly on a missed layup. A team physician cleared Irving to play and he returned in the fourth, but couldn't stop the Cavaliers from dropping their sixth straight game, 91-76 to the Pacers.
"When I went back it still didn't feel right," said Irving, who finished with 10 points, five assists and five rebounds in 35 minutes. "I thought the worst happened. I felt something pop in my knee. I was falling down around all over the place. It was a painful experience. I was praying to God everything was OK. I just have to hope for the best. We'll see what's going on."
Irving said he will have an MRI on Wednesday.
"It's probably something slight, if anything at all," Irving said. "I'm going to hope for the best, honestly. Right now, it's a little bit of a painful experience but it's something I'll get through."
Irving has been injury prone during his two-plus seasons in the NBA.
The former No. 1 overall pick has missed 38 games with a variety of injuries, including a broken nose, broken jaw, broken finger, sprained knee, sprained shoulder and concussion. He played in only 11 games as a freshman at Duke because of a foot injury.
One of Irving's goal this season was to play in all 82 regular season games. He's been durable this season despite sustaining a broken nose last month against Minnesota and playing with a protective mask. He also played last week after missing two days of practice with the flu.
The Cavaliers have reportedly been in talks with the Los Angeles Lakers about a trade involving center Andrew Bynum, who was recently banned from all team activities for detrimental conduct. The severity of Irving's injury could alter affect any plans the Cavs may have to alter their roster.
Bynum signed a two-year, $24 million contract with the Cavs in July, but only $6 million is guaranteed if the Cavs release or trade him by Jan. 7.
AP Sports Writer Tom Withers in Cleveland contributed to this report.