Anunoby was injured late in Game 2 of the Eastern Conference semifinals, in which he scored 24 points.
The Knicks hold a 3-0 lead in the best-of-seven series.
Anunoby was having another strong game Wednesday before appearing to suffer a leg injury and motioning to come out of the game. He went to the locker room area and did not return to the bench before the end of the Knicks' 108-102 victory.
Anunoby is averaging 21.4 points per game in the postseason while shooting 61.9% from the field and 53.8% from 3-point range.
The 6-foot-7 Anunoby, who is considered the Knicks' top defender, injured his hamstring two years ago in the second round as the Knicks were taking a 2-0 lead over Indiana. He missed the next four games and played just a few minutes in Game 7 as the Pacers rallied to win the series.
The Associated Press contributed to this report.
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