Knight could reportedly miss the season with the injury.
Knight, 25, tore the ACL in his left knee playing basketball in Miami. He averaged 11 points per game last season functioning mostly as a reserve.
Knight was the eighth pick in the 2011 draft, with the Pistons selecting him out of Kentucky. He has played for three teams in six seasons, traded to the Bucks and then to the Suns in 2014. He has struggled to latch on and find regular playing time, and was shut down on March 17 of last season despite being healthy.
In 2015, Knight had arthroscopic surgery on his left ankle.
For his career, Knight has averaged 15.2 points, 4.3 assists and 3.3 rebounds over 382 games.