The U.S. talk show host was enjoying a break during the taping of The Late Show with David Letterman when he started passing a ball to his stage manager, Biff Henderson, who is often involved in comedy segments of the TV programme.
But Letterman's last throw to his sidekick went wrong when Henderson moved to catch the ball and tumbled off the stage in front of the studio audience. Before he knew Henderson had been hurt, Letterman quipped, "I can smell a lawsuit."
Audience member Sheva Oliver tells the New York Daily News, "They cut the cameras and the band played for about 20 minutes and that's how we all knew it was serious."
The crew cut the taping and the 63 year old was attended by medics, who moved him onto a gurney and took him to Roosevelt Hospital in an ambulance.
Henderson was treated for a leg injury and released later that night (08Feb10).