In e-mails to the Los Angeles Times and Los Angeles Daily News, Scott Schenter, a Santa Monica, Calif., businessman, said the car is driven by Johana Michelle Beltran -- McKnight's girlfriend -- and that he helped purchase the Land Rover because Beltran's family had trouble qualifying for a loan.
"It is her car," Schenter wrote. "She makes the payments and she is responsible for insurance. The payments are a little over $500/month [not a big amount]."
McKnight has denied driving the car, but the Los Angeles Times said in a story that one of its reporters has seen USC's leading rusher driving the SUV several times.
The Times first reported the story Friday night.
Schenter also said he is a University of Washington fan who has "nothing to do with agents, marketing players or representing athletes" despite his ownership of the Web domain www.4joemcknight.com, which he says has not been renewed.
"I own so many Web site domains that I only purchased www.4joemcknight.com [didn't renew] because I thought it was clever along with the many other ones I own/owned," Schenter wrote in the e-mails.
Schenter said a company he founded in May 2008, USC Marketing, stood for "United States China Marketing," and that despite being an employee for the Los Angeles County Assessor's office, he would "rather be known for my expertise in marketing and finance ventures."
USC, already under review by the NCAA and Pac-10 regarding accusations that running back Reggie Bush and basketball star O.J. Mayo received improper benefits during their time at the school, is investigating McKnight's use of the vehicle.
If McKnight is in violation of NCAA rules, it could affect his eligibility. It is against NCAA rules for athletes to accept benefits from agents or marketing representatives, or to accept "extra benefits" based on their ability.
Despite being in attendance for a USC men's basketball game against Tennessee in Los Angeles on Saturday night, athletic director Mike Garrett was not made available to local reporters.
"I read the letter [by Schenter] and found it interesting," said a statement from Garrett, read by a Trojans spokesman to the reporters at halftime as Garrett sat next to him. "Our compliance people are handling the matter. I have nothing more to say."
USC plays Boston College in the Emerald Bowl on Dec. 26 in San Francisco.
Information from The Associated Press was used in this report.