NEW YORK (Reuters Health) - Many teenagers, especially girls, have some degree of "double-jointedness," a UK study suggests -- a sign, researchers say, that such flexibility is most often perfectly normal.
They also say their findings raise the question of whether so-called benign joint hypermobility syndrome (BJHS) is being overdiagnosed.
BJHS refers to extreme flexibility in the joints that is not caused by a serious medical condition, such as Marfan syndrome, an inherited condition that affects tissues throughout the body.
Often, people with the hypermobility syndrome have joint pain, but not always.
And there is controversy over how often the joint flexibility is actually the cause of that pain, explained Dr. Jacqui Clinch, a consultant in pediatric rheumatology at the Bristol Royal Hospital for Children in the UK and lead researcher on the new study.
One way to get a better understanding of joint hypermobility as a health "condition" is to see how common hypermobility is in the general population. But until now, there had been no good estimates because studies have been small, or only looked at select groups of kids.
In their study, Clinch and her colleagues found that of 6,000 14-year-olds they assessed, about 27 percent of girls and 11 percent of boys met the commonly used criteria for joint hypermobility syndrome.
Using the criteria, known as the Beighton score, doctors look at whether certain joints are hyper-flexible -- including whether the knees or elbows bend backward, the thumb can be flexed to touch the forearm, the pinkie finger can be bent backward past 90 degrees, and whether the person can place his palms on the floor without bending the knees.
In general, a Beighton score of 4 or higher -- meaning at least four hypermobile joints -- is the cutoff for diagnosing
Other factors can be considered, like whether a person has joint pain. But the condition may be diagnosed just based on the Beighton score, Clinch told Reuters Health in an email.
Based on these latest findings, that kind of flexibility is common, the researchers report in the journal Arthritis & Rheumatism.
"Our study has shown that 'double-jointedness' is very common in children," Clinch said.
Certain joints were especially flexible: 45 percent of girls and 29 percent of boys had hypermobile fingers.
And in the "vast majority" of kids, Clinch said, such flexibility causes no problems -- and may help some excel in sports or playing musical instruments that require supple joints and nimble fingers.
What's more, Clinch said, the findings suggest that the Beighton cutoff score may be too low for diagnosing joint hypermobility syndrome, or that it is not the right tool for assessing hypermobility in children.
"We feel that BJHS may be being overdiagnosed on the background of poor assessment tools," Clinch said.
The current findings, according to Clinch, offer a "true" estimate of joint hypermobility, at least among white children (reports suggest the rate is higher among non-whites). She said the challenge now is to zero in on the "small number" for whom loose joints may cause pain or other problems.
"In doing this we may need to look at a different, more sensitive tool to meaningfully measure joint hypermobility in the developing skeleton," Clinch said.
In cases where a child is thought to have BJHS, some form of treatment might be recommended -- such as exercises to strengthen the muscles surrounding the joints, teaching kids how to avoid hyperextending their joints or wearing a brace to support extra-mobile joints during certain activities.
According to Clinch, much remains to be learned about the health effects of hypermobile joints.
A "minority" of children with BJHS have recurrent joint dislocations that limit their activities, she noted.
But the role of hyper-flexible joints in chronic pain is contentious, according to the researcher. And there is currently no evidence, Clinch said, that these kids face a higher risk of arthritis later in life.
SOURCE: bit.ly/lqsB6w Arthritis & Rheumatism, online May 5, 2011.
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