The 30th overall pick in last year's draft was injured in the third quarter, when his knee buckled awkwardly while he tried to change directions. The slender guard immediately grabbed his leg and had to be helped to Cleveland's locker room.
Porter was on crutches as he left the trainers' room after the game. He was not available for comment.
Cavaliers coach John Beilein said the team hopes to learn more about the injury on Monday.
Porter entered Sunday averaging 8.6 points, 3.2 rebounds and 2.0 assists this season.
The Associated Press contributed to this report.