The midfielder had been offered a one-game ban at the Match Review Panel, but chose to contest the charge and risk a two-match suspension.
After 10 minutes of deliberation, the jury found Johnson guilty of misconduct, but deemed the force negligible, which was enough to leave the Cat free to line up in Saturday's massive match.
Johnson argued that North Melbourne's Scott Thompson had held him back from trying to contest for the ball, a claim the Kangaroo confirmed in his questioning.
"I then put my knee down in another way of trying to leverage myself to get away from him," Johnson said.
Johnson said he was surprised by Thompson's reaction, but the North defender later admitted he went into the game with a cracked rib and was wearing a guard.
Thompson said he didn't want to reveal his injury or "it would be targeted".
AFL counsel Nick Pane QC countered by arguing that the injury was not enough to suggest impact was insufficient.
Pane said if it was not reckless it was negligible, which would result in the same penalty.
"It is quite clear that kneeing in those circumstances falls in the wide meaning of misconduct," he said.
Umpire Brett Rosebury also gave evidence. He said he was around 20-25m away from the incident and that he saw it out of the corner of his eye. He said he ran back and told them to move on and get on with the game.
Rosebury added he didn't see anything that constituted a report and on reviewing the footage said he could have paid a free kick but wouldn't have laid a report.
