Yes. He probably has growing pains, the most common cause of leg pain in kids ages 3 to 12. (And yes, they're real!) The classic symptoms:

* Pain in the shins, calves, thighs, or behind the knees of both legs (not necessarily at the same time)

* Pain late in the day or at night, lasting minutes to hours, from mild to severe

* No redness, swelling, or any other visible change

* The pain comes and goes

* They're often worse when kids have been very active.

Doctors don't know what causes growing pains; they actually don't seem to have anything to do with growth. They may be related to a lower pain threshold, overuse, mental stress, flat feet, or loose joints.

There's no test doctors can do to confirm that a child has growing pains. We can, though, rule out something else. It's probably not growing pains if:

* The pain is in the joints

* It occurs in the morning and/or during the day, or more than two or three times a week

* Pain is on one side only

* There's redness, swelling, or a rash

* The child has a limp

* There's fever, fatigue, or other signs of illness.

To be safe, see your kid's pediatrician. If he does have growing pains --and he probably does --leg massage often helps. If it doesn't, try acetaminophen or ibuprofen, following the package directions.

Claire McCarthy, M.D. is the director of pediatrics at the Martha Eliot Health Center, in Jamaica Plain, MA, and a faculty member at Harvard Medical School. She's also busy raising five children.