By Genevra Pittman
NEW YORK (Reuters Health) - Double-jointed teens are more likely than their less flexible peers to develop shoulder, knee or ankle pain, suggests a large, new study from the UK.
Apart from the findings for those particular joints, researchers found no link between double-jointedness - also known as joint hypermobility - and any other types of pain, including back and neck aches.
"There is the assumption that these patients who've got joint pain who are found to have joint hypermobility, that the two are related," said the study's lead author, Jon Tobias, from the University of Bristol.
But the scientific evidence has been a bit more ambiguous, he told Reuters Health.
In his team's study, Tobias said, "The types of joints that were affected seem to be quite specific." That could explain why some other studies found no link between double-jointedness and a more general definition of pain, he added.
The new data come from a long-term study that originally recruited pregnant women in the early 1990s. Tobias and his colleagues measured joint mobility in about 2,900 of those women's children at age 13 or 14 and surveyed them about muscle and bone pain four years after that.
Just under 1 in 20 teens was double-jointed, based on meeting the standard of having at least six of nine joints - both thumbs, little fingers, elbows, knees and the trunk - that are more flexible than usual.
About 45 percent of study participants reported any type of recent bone or muscle pain during their second session. The proportion was similar among double-jointed and less-flexible teens.
When the researchers looked at specific joints, however, they found shoulder, knee and ankle or foot pain were all 70 to 80 percent more common among double-jointed teens. In total, between 6 percent and 10 percent of all teens reported pain in each of those joints.
"We think that might be a sort of mechanical thing, that the pain might be (from) overstretching the joints, and that's a particular problem if it's a weight-bearing joint," Tobias said.
The link between double-jointedness and knee pain, in particular, was especially strong in obese youth, the researchers report in Arthritis & Rheumatism.
For that reason, Tobias said the one piece of advice he would give double-jointed teens is to lose weight, if they're heavy.
Dr. Jennifer Moriatis Wolf, an orthopedic surgeon from the University of Connecticut Health Center in Farmington, said she has noticed people with joint hypermobility may not heal as quickly from sprains and strains.
"I suggest they try to avoid exaggerated positioning of their joints if they can," Wolf, who was not involved in the new research, told Reuters Health.
She agreed that very mobile joints such as shoulders and knees might be especially vulnerable to pain when overstretched and overloaded.
"Therapy and strengthening around the joints or general conditioning of the muscles around the joints can help in decreasing pain," Wolf said.
The authors of another recent study published in Arthritis Care & Research surveyed almost 13,000 older adults and found a "modest" link between double-jointedness and chronic, widespread pain.
Using a less strict definition of joint hypermobility, Matthew Mulvey of the University of Manchester, UK, and his colleagues found between 18 percent and 19 percent of double-jointed adults had chronic pain, compared to 16 percent of non-double-jointed people.
"Based on these data, it is difficult to suggest direct implications for clinical practice given the weak association observed between (joint hypermobility) and musculoskeletal pain," the research team concluded.
SOURCES: http://bit.ly/X3aPTQ Arthritis & Rheumatism, online February 28, 2013 and http://bit.ly/10qv6Uh Arthritis Care & Research, online February 11, 2013.