American Kathryn Mayorga has accused Ronaldo of sexually assaulting her in a hotel in Las Vegas in 2009, something the Portugal and Juventus forward has strenuously refuted.
German publication Der Spiegel first reported the claims, which also included the suggestion Ronaldo paid Ms Mayorga $375,000 in 2010 as part of a privacy agreement, preventing her from going public with the allegations. Ms Mayorga filed a lawsuit in an attempt to quash that agreement while Las Vegas police have re-opened an investigation.
Christiansen confirmed the payment was made to Ms Mayorga, but said some documents presented as evidence had been "stolen" and "completely fabricated", while Ronaldo described rape as an "abominable crime" within an October statement he issued to "firmly deny" the accusations.
On Thursday, the Wall Street Journal reported that police in Las Vegas had requested a sample of Ronaldo's DNA.
And in a statement sent to Omnisport, Christiansen said: "Mr Ronaldo has always maintained, as he does today, that what occurred in Las Vegas in 2009 was consensual in nature.
"So it is not surprising that DNA would be present, nor that the police would make this very standard request as part of their investigation."
Ronaldo, 33, has scored a league-high 14 goals in Serie A and 15 in all competitions for Italian champions Juve this season, having arrived from Real Madrid in July.