Eagle-eyed readers noticed something funny about Csonka's right hand: He appeared to be extending his middle finger. And all these years later, Csonka was asked about that cover in an interview with Phin Phanatic:
From George in Maine: In the 1972 SI cover with Jim Kiick, you two appear to be laughing, not just smiling. Your right hand is posed nicely, was that a message to anyone specifically or was that just having a little fun?The postscript to the story is that three years later, Csonka posed for a similar SI cover. This time he didn't flip the bird.
LC: That photograph was made in jest for my private use via an agreement with the photographer. Somehow it slipped through the censors and ended up on the cover of Sports Illustrated. It was an accident, it was not intended for anyone specifically.