Growing pains are the most common childhood musculoskeletal condition resulting in frequent visits to healthcare professionals. For two centuries, its incidence, cause and treatment have baffled the health and medical community.
There is no single diagnostic test for growing pains. As a result, it continues to be diagnosed more by exclusion than inclusion of symptoms. Namely: intermittent (non-persistent) aches of muscles (not joints) in both legs presenting later in the day or evening (disappearing by morning) in an otherwise healthy child generally between the age of three and 12 years. There are usually no abnormal findings on physical exam, imaging and lab investigations.
French physician Marcel Duchamp first coined the term "growing pains" in 1823, but many now regard it as somewhat of a misnomer since physical growth as a source of pain is disputed. Despite this, the term remains in common usage. This in itself makes it difficult to more clearly define the nature of the condition.
Vague definitions such as "discomfort, commonly of legs, of unknown cause" contribute to the confusion surrounding this largely misunderstood condition. Evaluating children's pain is a difficult task. Children with pain find it hard to articulate exactly when and how the pain started, and even older children and adolescents struggle to tell us the type of pain they are experiencing.
What causes growing pains?
The origin, cause and effect of growing pains are unknown. Proposed theories, which are steadily being debunked, include muscle fatigue in active children, biomechanical factors such as flat feet, mental or emotional causes, or as part of a broader pain syndrome. Historically, girls have been thought to be more susceptible, but this is unsubstantiated.
More recent theories include altered pain threshold, decreased bone strength, excess flexibility known as joint hypermobility, greater body weight, parental history of arthritis or family history of growing pains – which might suggest a genetic link. Twin research shows some evidence of genetic susceptibility to growing pains and an association with restless legs syndrome.
One of the most obvious yet contentious causes of growing pains is growth itself. Parents report an association between growing pains and increased growth in 35 per cent of cases. An experiment in lambs showed 90 per cent of bone elongation occurred when the lambs were lying down and almost no growth occurred during standing or walking. The authors concluded that similar growth patterns may occur in children, which could support the concept of night-time growth and a link to growing pains.
One problem with this theory is that while all children sleep and grow, not all children suffer growing pains. Instead, it could be that the rate of growth, which we know is episodic for each child (think "growth spurts") and can vary between children, may be a more plausible explanation why only a proportion of children experience growing pains.
How common are they?
Difficulties with definitions make population estimates hard, but recent research suggests growing pains occur in between 3 per cent and 49 per cent of children.
A robust prevalence study in South Australia concluded they affect 37 per cent of children aged four to six years. So, about one child in every three is affected. The amount of distress varies from awakening and complaints of leg pain to crying and reduced quality of life.
What can be done?
Unsurprisingly, because growing pains are largely enigmatic, they are poorly managed. A common feature of growing pains is their spontaneous resolution, even if this occurs after a period of years. Thus any management is really focused only on controlling symptoms.
There is only one randomised controlled trial that offers evidence for the treatment of children with growing pains. This small trial of 18 children who performed stretching of thigh and calf muscles for 10 minutes twice daily over 18 months showed faster improvements in symptoms when compared to the 16 children in the control group who used standard treatments such as massage and aspirin. However, the number of growing pain episodes reduced substantially in both groups.
Massage seems somewhat helpful and can be supplemented in more severe cases by the application of heat and mild oral analgesics. If the child has atypical symptoms, such as persistent joint pain, it's important to carefully rule out more serious conditions.