Lions general manager Martin Mayhew said today that Johnson underwent "minor" knee surgery last week and on a mangled finger.
"He played the entire season with a finger really that was pointing perpendicular from his body the whole season," Mayhew said. "He's trying to catch the ball like that. He would never complain about that, but certainly that was a factor, I think, in the way he played."
Johnson finished third in the NFL with 1,492 yards receiving and also caught 84 passes and 12 touchdowns, but did drop eight passes, according to STATS, LLC, including two key ones in a Monday night loss.
Asked whether Johnson's surgery was related to a PCL injury, Mayhew said, "No, it was just a minor scope. He's going to be fine."