Approximately one in three children between the ages of 4 and 6 develops growing pains, according to new research.

Previous estimates of the frequency of growing pains have varied widely, and few have focused on younger children, the study’s lead author told Reuters Health.

“This was quite a surprise,” said Dr. Angela Margaret Evans of the University of South Australia in Adelaide.

“It has been reported as opinion that young children are the most affected but until now they have been the least studied group. There is still a lot for us to learn about growing pains,” she added.

For instance, Evans explained that the cause of growing pains remains unknown. However, the pains do follow some general rules: they occur mostly in the legs, appear in both legs, begin in the late afternoon or evening, and recur intermittently. The pain occurs in the muscles rather than joints, and is not related to injury.

To investigate the rate of growing pains in young children, Evans and her colleagues asked 1445 parents whether their children had ever experienced aching legs, when and how often those pains occur, and their severity.

Approximately 37 percent of children between the ages of 4 and 6 had likely experienced growing pains, the researchers report in the Journal of Pediatrics.

Evans explained that many former estimates have varied widely because they used different definitions for growing pains and grouped children of different ages together.

She added that a few theories have tried to explain why growing pains occur. Some experts believe that the pains occur because of muscle strain after increased activity, while others have proposed that the pains arise from anatomical problems in children, such as flat feet or knock-knees. Still other experts have suggested that the pains stem from a psychological factor, such as an increased sensitivity to pain.

The best-tested remedy for growing pains involves muscle stretching, Evans noted, but parents often also resort to acetaminophen, massage or hot packs, “which may also help.”

Evans noted that she hopes these findings help encourage researchers to investigate the true cause of growing pains and the best methods for easing children’s suffering.

“It really shows that we need to learn what causes growing pains and how to best manage it as it can potentially use up a lot of health resources,” she said.

SOURCE: The Journal of Pediatrics, August 2004.