McGee suffered the injury on Aug. 18 against the Astros.
"I felt it on [his second-to-last] pitch and it felt a lot different," McGee said. "I threw the last pitch and felt the same thing. Kind of knew something was wrong from there on. So when I got into the dugout I talked to the trainers and it kind of went from there."
McGee said once he pushed off the rubber, "It felt like it kind of opened up and something was wrong."
"The next day, I was real sore around the joint and the knee, so I flew back to Tampa and saw [team orthopedic Dr. Koco Eaton] and kind of went from there," McGee said. "Initially it looked a little worse on the MRI. But when we got in there it turned out a lot better."
McGee returned to the Tampa Bay area on Wednesday and Eaton performed the surgery on Thursday at St. Anthony's Outpatient Center in St. Petersburg.
McGee experienced knee pain in his left knee in 2010 and has worn a knee brace since.
"Kind of the same thing happened in 2010 and I only missed a few starts," McGee said. "So it's a little worse than last time. But I'm glad I had [the brace] on there, it could have prevented further injury, too."
Bill Chastain is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.