Growing pains (GPs) and restless leg syndrome (RLS) are often confused with each other, but are different conditions. GPs are not dangerous and are the most common form of episodic childhood pain of the musculoskeletal system.
It is estimated that up to 4 in every 10 children, both boys and girls, between the ages of 3 – 12 years will experience GPs at least once. The etiology is unknown, but several theories involving flatfeet, hypermobility, reduced pain threshold, lower bone strength and psychological issues are all being studied as contributing factors.
RLS manifests as an uncomfortable sensation in the legs and creates the urge to move the legs around to escape the discomforting sensation. The legs are primarily affected, but the arms and other areas of the body may also be affected as well. Approximately 10% of the population is affected with a greater prevalence among women.
Like GPs, the cause of RLS is still unknown. However, it is speculated that there might be a familial linkage, since approximately 50% of those affected have family members with the same problem. Moreover, diseases like Parkinson’s and diabetes as well as some medications and pregnancy are known exacerbating factors.
The criteria for diagnosing GPs and RLS are different. Unlike RLS, there is no universal definition for GPs. 2 prominent groups adopted diagnostic criteria from Peterson, which were then modified. One of the explanations for this was that Peterson only offered a general description of GPs as opposed to actual diagnostic conditions with enumeration of exclusion and inclusion factors.
According to Peterson, GPs represent intermittent pain that occurs late in the day and is localized in the leg and thigh muscles and may be associated with a restless feeling. The pain may be accentuated during periods of increased activity and may awaken the child from sleep at night, but is gone by the morning.
Children with RLS must meet criteria that includes an urge to move the leg(s) that may or may not be associated with discomfort or pain. These symptoms are typically worse when at rest (i.e. lying or sitting) in the evening and the night. A patient with RLS may have temporary relief by moving around in bed or walking.
Disorders, which include cramps or discomfort due to position, may mimic RLS and thus should be excluded when questioning the patient. It is important that the child describes the symptoms in his or her own words and definite diagnosis is met when all of the mentioned signs and symptoms are experienced.
GPs tend to be strictly bilateral (i.e. occurring on both sides of the body), while RLS may occur unilaterally or bilaterally. Likewise, RLS may present with varying degrees of discomfort within the legs, including pain, whereas GPs are identified as universally painful. However, painless and/or unilateral GPs are not unheard of.
Because both conditions are capable of inducing pain, it is not surprising that many children who actually have RLS may be misdiagnosed at first with GPs and vice versa. Unlike in RLS, children with GPs do not experience relief from discomfort when moving the leg around or walking.
Similarities between GPs and RLS
GPs and RLS present with some similar clinical findings that can easily lead to the two being confused with each other. To name a few, both have a similar age of onset, range of duration and predominance during the nighttime. Children with these conditions do not typically experience any limitations to activity or any limping.
Furthermore, there is no laboratory evidence of underlying pathology in either condition and there are no physical and neurological anomalies found on examination. In addition to this, both disorders tend to present with symptoms that last for at least 3 months and do not cause a general lack of wellbeing aside from their defining clinical features.