The 34-year-old Johnson, who has been raising money for disabled athletes, faces months of rehabilitation, the Anchorage (Alaska) Daily News reported. He has had two operations in four days.
Johnson was competing in the world telemark free skiing championships at the Alyeska Ski Resort near Anchorage. He was in 14th place after his first run and text-messaged a friend that he was planning to "go big" on the second on Saturday.
A friend and skiing partner, Dave Magoffin, told the newspaper that the cliff jump was Johnson's fallback, that he had probably been planning to stay on a band of snow that proved to be ice where he could not hold an edge.
Johnson, who lives near Denali National Park, supports his skiing by guiding white-water rafting trips in the summer and driving a bus at a Utah ski resort in the winter, the Daily News said.