He underwent the surgery in Los Angeles. He will be re-evaluated in four to six weeks, the team said.
The Thunder are scheduled to begin training camp on Sept. 26.
Patterson, 28, agreed to a three-year, $16.4 million contract in July. He is expected to start at power forward for the Thunder, as Domantas Sabonis was traded to the Indiana Pacers in the deal that sent Paul George to Oklahoma City.
Patterson was largely a reserve the past four seasons for the Toronto Raptors, averaging 7.6 points and 4.8 rebounds in 25.2 minutes.
He spent his first 2½ NBA seasons with the Houston Rockets, who selected him with the 14th overall pick in 2010 out of Kentucky. He spent parts of two seasons with the Sacramento Kings before being traded to Toronto in December 2013 as part of the Rudy Gay deal.