With under three minutes left in the third quarter, Thompson was running in transition with teammates DeMarcus Cousins and Stephen Curry. Curry threw a pass to Thompson, who took two steps and leaped for a dunk attempt.
Raptors guard Danny Green tried to block the shot and made contact with Thompson, slightly altering his landing spot. The All-Star guard landed awkwardly and his left knee buckled under his weight.
Thompson appeared to be in significant pain and was helped to the locker room. Before making it to the training room, the guard reversed course and limped to the court to take two free throws.
Thompson then left the game immediately after the foul shots and was ruled out for the contest. He was shown exiting Oracle Arena on crutches.
Thompson, who previously sat out Game 3 with a hamstring strain, had 30 points and five rebounds in 32 minutes before leaving the game.