Growing pains are a bigger problem than thought and affect one in three young children, Australian research suggests.
Growing pains appear to be linked to activity
Parent questionnaires revealed nearly 37% of 1,445 children aged four to six years had recurrent aches and ailments described as typical growing pains.
The University of South Australia team is testing whether the pain might be caused by different foot postures.
The team's findings have been published in the latest issue of the Journal of Pediatrics.
People have known for years that children and adolescents can complain of painful legs, particularly at night, as they are growing up.
Previous estimates of the extent of the problem have varied enormously because of the different age ranges studied, but suggest it mainly affects young children.
To get a better idea of the true incidence, child development expert Angel Evans sent questionnaires to 25,000 parents of children aged four to six living in Adelaide.
Features of growing pains
Pain occurs in both legs
Pain occurs in the muscles and not in the joints
Pain occurs late in the day or at night time
The child is otherwise well
The pain is linked with increased activity levels
The parents and siblings are likely to have experienced similar pain as children
A third of the parents who returned the questionnaire said their child experience growing pains to the point that they were seeing a health professional or taking pain medication.
Ms Evans said: "As a clinician I was seeing a lot of children with growing pains. I realised we had no idea of how much of a problem this potentially is.
"This shows it affects a third of children aged four, five and six, which is very high.
"It has also been estimated in other studies that children with growing pains who frequently see their medical or other health practitioners can take up between 5% and 7% of health care resources, which is considerable," she said.
There is no consensus as to what causes the pain but she said there were three theories.
"The first is it's due to fatigue of the leg muscles after increased levels of exercise or activity. The next is that it's an emotional pain response and more likely in some families, and the final theory is it's related to anatomy - things like flat feet," she said.
Her team is testing the latter theory by comparing the foot posture of 192 children, some with growing pains and some without.
The results should be ready in a couple of months.
Whatever the findings, she said a proven treatment was available but many parents were not aware of it.
"The best management technique to date is a muscle stretching programme that was developed in Canada in 1988, yet it's infrequently used or recommended," she said.
This involves stretching the calf and thigh muscles of each leg twice for around 20-30 seconds each time, usually towards the end of the day or night time when growing pain tends to be at its worst.
"Parents can do this, or they can use what is recommended and practiced by other parents which is hot packs, paracetamol or rubbing the child's legs," she said.
Dr Michael Briggs from the University of Manchester Wellcome Institute, who had conducted research into children's bone diseases, said: "Certainly, in my experience, you tend to think of children with growing pains as rather rare diseases, but in fact they are a lot more common than people have thought in the past."