The 20-year-old Northern Irishman saw a specialist on his return from Dubai, where he finished sixth on Sunday in the defence of his Desert Classic title.
McIlroy has been working with South African physio Cornell Driesson to try to manage the discomfort he feels occasionally.
“He just needs to rest for a day,” said his management spokesman, Martin Hardy.
Now world number seven — three places ahead of fellow Irishman Pádraig Harrington — McIlroy has been told the problem could be linked to the hip movement in his swing.
“They go backwards and then forwards and that puts a little strain on the lower back,” he said.
“I do all the exercises I can to make everything stronger around the joints and it is a matter of resting and managing my schedule so that I am not playing too many weeks in a row.”
McIlroy has taken up US Tour membership this season and next week is the first of five events there before the US Masters in April.
Meanwhile, the Volvo China Open will be part of the European Tour again this year, with prize money rising to €1.8m when it is staged at Jinji Lake near Shanghai on April 15-18.
Australian Scott Strange’s one-stroke victory in Beijing last year saw him become the sixth different winner of the Volvo China Open in six years, and qualified him for the Volvo World Match Play in Spain.
The event comes the week after the US Masters at Augusta and is part of a Tour double-header in Asia, being followed by the Ballantine’s Championship in South Korea.