The Suns said Tuesday an examination by team doctor Tom Carter determined the surgery would be required.
Knight’s playing time diminished as last season progressed and the Suns chose to go with younger players. He appeared in 50 games, averaging 11 points and 2.4 assists.
Knight came to Phoenix in a three-team trade with Milwaukee and Philadelphia in 2015.
He has been unhappy with his role and the Suns had been expected to try to trade him, a deal that would be complicated by his contract. He has three years and about $44 million left on his contract.