However, the explanation for the injury was a little more mundane as the Australian said he fell in his hotel bathroom earlier in the day.
"We've had judo then MMA (Mixed Martial Arts) - we're going through the martial arts," he joked when asked about the injury at the Hurlingham Club in London.
"Actually I slipped over in the hotel this morning. I walked out of the shower, I forgot to shave, and I went over."
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Jones was accompanied at the launch by hooker Dylan Hartley, who was confirmed as captain and is set to start England's opener with France on Feb. 4 despite not playing a match since being banned for a high tackle in a club game last December.
"I feel fresh, fit and focused," said Hartley. "I've had some time out – I know where I need to be."
When Hartley was asked if he had had much previous experience of preparing for a big game after a long spell on the sidelines, Jones interrupted. "Sixty weeks mate," he said, laughing, in reference to the hooker's accumulated ban time. "He's a world expert."
Jones, who oversaw a perfect year of 13 wins having taken over from Stuart Lancaster, is seeking a second successive Six Nations Grand Slam.
(Editing by Ken Ferris)
