Leg pains seem to occur in almost all children at some stage during growth. They are often known as growing pains though growth itself is not painful. We call these Benign Leg Pains because the pains do not cause long term problems even if they can be quite distressing at the time. There are two different patterns of leg pains. The first seems to occur in a very active child in the evening after excessive running about. The second occurs in the middle of the night when the child awakes screaming in pain, which they may localize to a foot or knee or hip.
WHAT CAUSES BENIGN LEG PAINS?
No one knows for certain. We do know they are harmless. The pains that occur after exercise are probably the body's way of protecting the growing bones against overuse damage. Unlike adults, children have gristle plates scattered through their bones to provide growth. Because gristle is weaker than bone, there comes a point in a very active child when to continue running about will cause damage to these growth plates. The body protects itself against such damage with pain. During growth spurts these plates are weaker so the pain starts sooner. This is why the pains were called growing pains.
The pains that occur in the middle of the night are frightening because they seem so severe but they are just cramp. We all know how painful cramp can be! Cramp occurs when muscles are not getting enough blood. Your blood pressure can drop very low during sleep. If the child has been very active during the day their hard-worked muscles swell up a little. Muscles are covered in a tight sheath which prevents swelling, so instead the pressure in the muscle increases. This means the blood pressure may not be enough to supply the muscle when it falls normally during deep sleep. Alternatively the inflow of blood may be restricted because the child sleeps with their legs folded under themselves.
WHAT CAN BE DONE ABOUT THE PAIN
There are no magic wands. Leg pains caused by over-activity will not occur if the child reduces their level of exercise to minimize the pain. This will vary depending on how fast they are growing. Remember that the pain is nature protecting your child from more serious harm. Painkillers may allow the child to do more damage to themselves.
The night cramps are best managed by rubbing the sore leg and reassurance. The pain usually settles before a painkiller has time to work since this can take up to half an hour. Giving a painkiller before bed does not help because no painkiller is strong enough for cramp. In any case the pain helps by raising the blood pressure which relieves the cramp more quickly. Going in at your bedtime to untangle folded legs helps to reduce the number of attacks. Eventually the child grows out of the cramps but this may not be till age 9 or 10.
CAN LEG PAIN BE MORE SERIOUS?
Yes. A persistent limp or pain occurring day and night might be investigated further. An X-ray of the hips can exclude rare conditions such as Perthes' disease or a Slipped Upper Capital Epiphysis. These conditions may be suspected if your GP has noted abnormal movement of the hips. Knee pain can come from a hip problem. Localized pain and swelling should always be investigated.
These conditions have been excluded as the cause of your child's leg pains at present but if the pattern changes in the future you may wish to see your GP again.