What causes growing pains?

What the evidence says

Growing pains are really common, but here's a surprising fact: doctors don't actually know what causes them. And despite the name, they are not caused by your child's bones growing. Growth itself happens too slowly and gently to cause pain, even during a growth spurt.

So what might be behind them? One idea is that active kids simply tire out their leg muscles during the day, and the ache shows up later at night when muscles relax. This is called the fatigue theory. Another idea, the growth theory, suggests that bone growth sends out nerve signals that become more noticeable at night when there are fewer distractions, possibly linked to growth hormone released during sleep.

Other researchers have looked at things like weaker bones, flexible joints or flat feet, low vitamin D levels, or a child simply having a lower pain threshold than other kids. Some studies also find a link with stress, anxiety, or family patterns of pain, since growing pains sometimes show up alongside stomach aches or headaches. None of these theories fully explains every case, and scientists say more than one factor might be involved.

The good news is that whatever the cause, growing pains are harmless. They tend to affect both legs, especially thighs and calves, happen in the evening or at night, and are gone by morning. Kids can usually still run around and play normally the next day.

Because the cause is unclear, there's no specific way to prevent them. Gentle massage, a warm cloth, and children's pain medicine like acetaminophen or ibuprofen can help on bad nights. If the pain is in one leg only, involves a joint, causes limping, swelling, fever or weight loss, it's worth seeing a doctor since that's probably not growing pains.