Lions wide receiver Calvin Johnson has been bothered by a knee injury for much of the season and a report Sunday indicates doctors think surgery is necessary to clear up the problem this offseason. Adam Schefter of ESPN reports that Johnson has a sprained knee with “loose bodies” in it and that doctors have recommended an operation after the season. The final call will be Johnson’s, though, and the players hasn’t made a call yet. Deadspin recently had a report about Johnson that said he had a partially torn PCL in the knee, although neither Johnson nor anyone else from the Lions has offered a specific comment about the nature of the injury.