NEW YORK — I'm lucky: When I hear the phrase "growing pains," I think of Kirk Cameron, not night aches. I never suffered from growing pains as a child, and as far as I can tell, my 2-year-old doesn't have them yet either. So sometimes I wonder: Are growing pains real? If so, what causes them? And how do I make sure my kid never has them, because I really don't need another reason for screamy 3 a.m. wake-ups?
Growing pains are real — in fact, they're pretty common. Estimates vary, but one Australian study found that as many as 37 percent of 4-to-6-year-olds experience these recurring aches, which typically afflict a child's lower limbs in the afternoon or at night. Bizarrely, though, growing pains actually have nothing to do with growing — more on that later. And while they are nothing to worry about and usually disappear by the age of 14, growing pains can be confused with more serious health problems — so it's good to know what they are and what they aren't.
The term "growing pains" first appeared in a book penned in 1823 by a French doctor, but since then physicians have realized that the peak of these pains, which is at around age 6, doesn't correspond to a period of rapid growth. (A quarter of a person's total growth actually happens during puberty). So it's unlikely that growth has anything to do with growing pains, at least directly. But despite attempts to come up with more accurate monikers (such as "noninflammatory pain syndrome of early childhood"), the old name stuck.
How frequently kids experience growing pains varies — some never get them, others get them five times a year, and a handful of poor souls have them every night. But timingwise, there are a few general rules. First, growing pains usually first appear during the preschool years. "If a child is 8 and all of a sudden has pain at night, it is not growing pains," explains Barbara Ostrov, a pediatric rheumatologist at Penn State University. Second, growing pains only happen in the afternoon or at night, so kids who complain of pain during the day or who wake up stiff or sore in the morning are almost certainly not experiencing growing pains. Most of the time, the pains disappear by around age 14, but some kids will have them throughout their teen-age years.
Growing pains are "bilateral," too, in that they typically affect both sides of the body. This doesn't mean that both sides have to hurt every time — the right leg might hurt one night, and a few days later the left one will act up — but kids who only ever get pains on one side probably aren't having growing pains. And growing pains aren't visible. Your kid might be screaming his head off about his shin, but you should never actually see anything wrong with his shin. If you do — if you see redness or swelling or bruising, for instance — you should take your little one to the doctor, pronto.
So, the definition of "growing pains" is based on when and where the pain happens, not on what causes it. And even today, no one is sure what produces growing pains, but there are several theories backed by (limited) research, and together they suggest that growing pains might have a range of physiological causes. One possibility is that kids who get growing pains have abnormally low pain thresholds. In a 2004 study, Philip Hashkes, at the time a pediatric rheumatologist at the Cleveland Clinic, tested the pain thresholds of 44 children with growing pains by putting pressure on various parts of their bodies, including points that are particularly sensitive to individuals who have chronic pain syndromes like fibromyalgia. After conducting similar tests on 46 children who didn't have growing pains, Hashkes found that much less pressure was needed to incite pain in the children who had nightly growing pains.
Growing pains could in part be the result of overactivity, too. This theory meshes with parental observations that growing pains are often worse on nights after sports practices. These aren't your typical post-workout pains, though — kids are much more at risk for true sports overuse injuries, such as shin splints, in part because growing bones don't handle stress very well. In another study, Hashkes measured, using ultrasound, the bone densities and qualities of 39 kids who experienced growing pains and found they were lower than average. The density and quality of bone drops when it has been overused without having a chance to recover, so the findings suggest that some growing pains may be associated with too much running around. But some researchers aren't convinced by the overuse theory, in part because growing pains often start suddenly in the middle of night, and overused muscles should ache more consistently.
Still, a small 1988 trial found that regular stretching does appease growing pains. Doctors at the Children's Hospital of Eastern Ontario in Canada randomly split 34 kids with growing pains into two groups. The parents of the kids in the first group were taught how to stretch their kids' quadriceps, hamstrings and calves, and were told to do so every morning and evening for 10 minutes. The second group of parents were told to rub their kids' legs when they hurt and to give them painkillers when needed. Nine months later none of the kids in the stretching group were experiencing growing pains, while the kids in the other group were still suffering, on average, about two episodes of pains a month.
Other researchers have proposed that growing pains are sometimes the result of underlying anatomical problems or differences. Double-jointed kids, who are at a heightened risk for fibromyalgia and musculoskeletal disorders, are more likely to have growing pains, for instance. So, it seems, are kids with pronated (flat) feet, which can cause muscle imbalances and fatigue. One small trial found that shoe inserts reduced the severity and frequency of kids' growing pains within three weeks. When doctors took out their shoe inserts, the pain came back in most of the kids. But it's hard to know how much we can conclude from this trial and the stretching one. The children knew they were undergoing a form of treatment, so their improvement could have been in part the result of the placebo effect (which can, it seems, happen to kids) — they may have felt better because they were being treated, but not necessarily because the treatment worked.
Finally, some doctors have pointed out that growing pains are, for some reason, more common in emotionally instable children. In a 1951 paper, for instance, researchers noted that kids with growing pains were "frequently irritable, nervous, afraid of the dark." The implication seems to be that growing pains are either a reflection of emotional problems or perhaps even caused by them, but it's hard to identify the chicken and the egg here: I would be nervous and afraid of the dark, too, if nightfall brought extreme pain.
So, when your kid wakes up in the middle of the night screaming her head off about pain in her legs, how can you be sure she is experiencing growing pains and is not, like, suffering the onset of some horrible disease? Generally speaking, if pains conform to the strict definition of growing pains — if they happen only at night, if they're on both sides, and if they're invisible — your kid is probably fine. Benign bone tumors, often confused with growing pains, usually only cause pain on one side; arthritis (yes, kids can get arthritis) usually causes redness or swelling and often is worst in the morning. Restless legs syndrome, which a study suggests affects 0.5 percent of kids and 1 percent of adolescents, is characterized by a strong desire to move the legs that is sated once that's been done. Parents who are worried about their kids may want to ask for lab tests like X-rays and blood tests to rule out other problems, but the vast majority of time, growing pains are growing pains — they're harmless.
This doesn't necessarily mean they have to be suffered night after night, though. Painkillers like ibuprofen or acetaminophen often do the trick (and you can give them pre-emptively, at bedtime, if your child's pain follows predictable patterns — like if it's always the night after gymnastics practice). Massaging the aching area can help. It might be worth stretching your kids' legs in the morning and at night to see if it makes a difference, too. And if things get really bad, consider a visit to a podiatrist to see if your child might benefit from orthotics. But if nothing works, keep reassuring your child — and yourself — that growing pains do one day go away. Just like the television show. Hey, at least your child doesn't have to endure that.
Moyer is a science writer living in Brooklyn, N.Y. and is Slate's parenting advice columnist.