He played college football for the Georgia Bulldogs and was selected by the Panthers in the third round of the 2007 NFL draft.

Johnson attended Hawkinsville High School, where he was a three-sport athlete in football, basketball and track.

As a senior, he recorded 16 sacks and 30 pressures while leading his team to the Class A State Championship, where he returned an interception 83 yards for a touchdown.

In track & field, he competed as a member of the Hawkinsville relay squads, recording personal-best times of 43.27 seconds in the 4x100 and 3:42.47 minutes in the 4x400.

[7] [8] During Johnson's rookie year (2007), he appeared sparingly due to playing behind established veterans like Julius Peppers and Mike Rucker.

According to ESPN the Magazine, he was the highest paid player in the NFL during the 2011 season with a total salary of $34M.

[16] On December 1, 2017, Johnson was suspended for four games due to violating the league's policy on performance-enhancing substances.