 Is Hypermobility a Factor in Fibromyalgia?
IS THERE A DISADVANTAGE TO BEING HYPERMOBILE?
In this issue of The Journal, Karaaslan and colleagues question the association of hypermobility and fibromyalgia (FM)1. When adhering to strict American College of Rheumatology (ACR)
criteria for a diagnosis of FM2, they observed an equal frequency of hypermobility in patients with FM and controls, whereas there was an increased frequency of hypermobility in subjects complaining
of widespread pain. Thus they conclude that hypermobility likely plays a role in musculoskeletal (MSK) pain in some individuals, but not necessarily in FM.
Hypermobility has fascinated rheumatologists for decades. Benign hypermobility has been recognized as a normal variant of elasticity of connective tissue3, or less commonly a manifestation of a
definitive disease process such as Ehlers-Danlos syndrome. The diagnosis of hypermobility is made clinically, without need for costly or invasive testing, and is traditionally given with the
reassurance that ligamentous laxity is of no important consequence to the individual. This clinical wisdom is, however, based mostly on anecdotal experience, rather than scientific evidence. How then
may there be a link between hypermobility and widespread MSK pain or FM in particular?
FM, in contrast, remains a puzzling disorder. Ten years after its acceptance as a definite entity with established criteria2, FM continues to defy our understanding. Many possible pathogenic
mechanisms for FM have been explored with either conflicting or negative results. The most prevalent current hypothesis is that FM is a dysregulation of central pain processing mechanisms and
neuroendocrine dysfunction4; however, additional factors that might influence initiation or perpetuation of symptoms are likely important. The reasons why disordered pain mechanisms should manifest
predominantly as pain in the MSK system are also unknown. Factors that might contribute to localization of pain to the muscles and tendons in FM are therefore important, but largely unknown.
For this reason a link between hypermobility and FM has been suggested. The tender points, which are the only abnormal physical sign on examination in FM, are located mostly at musculotendinous
sites2. Tendons and ligamentous structures, which play an important role in stability of joints, are exposed to high loads and stresses during movement and activity. The overall integrity of the MSK
mechanism is dependent upon a composite effect of intact ligamentous structures as well as good muscle tone. It is thus reasonable to postulate that excessive laxity of ligaments may predispose an
individual to repeated microtrauma during even normal activity. A possible reason for recurrent joint trauma in hypermobile persons may be the recently demonstrated impairment of proprioception noted
in both small and large joints5,6. It therefore follows that recurrent microtrauma to ligamentous structures in some hypermobile individuals will lead to repeated pain experience and may trigger
disordered pain responses.
IS HYPERMOBILITY MORE COMMON IN THE RHEUMATOLOGY CLINIC THAN IN THE GENERAL POPULATION?
Prevalence rates of hypermobility vary depending upon the population being examined, and range between 5% in Caucasian adults3 to rates as high as 38% in younger Middle Eastern women7. Observed
rates of hypermobility are generallly higher in the rheumatology clinic, with reports ranging from 3%8 to 15% in mostly Caucasian patients9,10. The easy to perform clinical assessment of mobility has
been used since the mid 1970s11, but may not indeed be truly reflective of clinically significant mobility status. No allowances are made for the expected change in mobility with aging, or the
specific location of hypermobile joints. Excessive mobility of large joints such as the shoulders, hips, or knees may have different consequences from hypermobility of the small joints of the hands.
The higher rate of hypermobility observed in the clinic setting adds to evidence that hypermobility may play a role in MSK pain in some individuals. There is therefore a need to explain further the
identifying characteristics that predispose hypermobile persons to MSK pain.
HYPERMOBILITY AND MUSCULOSKELETAL PAIN
Since the earliest reports of musculoskeletal problems associated with hypermobility by Kirk, Ansell, and Bywaters in 196712, rheumatologists have pondered whether hypermobility is simply an
interesting clinical finding or does have adverse impact upon skeletal and muscular structures. Population studies of Finnish schoolchildren13, rural Africans14, and healthy North American blood
donors3 have not revealed any MSK consequences of hypermobility, whereas rheumatology clinic studies support the link between loose ligaments and MSK pain9,10,12,15,16.
Although there have been reports linking hypermobility and osteoarthritis9,12,15, a more immediate question might be the association of hypermobility and soft tissue complaints. It seems
reasonable to hypothesize that loose ligaments may lead to skeletal structural instability, and predispose the body to repeated minor or more serious traumatic episodes. Twenty-one of the original 24
hypermobile patients described by Kirk and colleagues had pain that was particularly associated with overuse12. A study of military recruits further supports the concept that excessive physical
activity leads to musculoligamentous lesions in hypermobile subjects17.
Hypermobility was the primary cause of MSK pain in most of the 6% of children presenting to a pediatric clinic18, and we have reported an association of hypermobility and soft tissue rheumatism in
the rheumatology clinic10,16. The discrepancy noted in symptom reporting by hypermobile persons in the clinic and in population studies needs to be addressed. The frequency and degree of physical
activity is probably an important factor. It is possible that a baseline level of reduced physical activity with bursts of more vigorous exercise may be detrimental, particularly in hypermobile
individuals. The population studied by Birrell were mostly peasant farmers and traders in a rural area of Nigeria, and were likely more continuously physically active than their average Western
counterparts14, thus explaining the absence of MSK complaints in those who were hypermobile.
THE ASSOCIATION OF HYPERMOBILITY AND FM
We and others have questioned whether any predisposing mechanical factors may be operative in the development of FM. The possible earliest association of hypermobility and FM was noted by Kirk in
196712. Five of 24 hypermobile patients complained of widespread pain, in the absence of some other rheumatological process12. We previously reported an association of soft tissue rheumatism and FM
in particular in hypermobile patients in the rheumatology clinic10,16. Three of 20 hypermobile patients reported by Bridges had a primary diagnosis of FM9. A number of studies have reported increased
frequencies of hypermobility and FM, ranging from 13% in Israeli schoolchildren19 to 40% in adults in the rheumatology clinic20,21. Of particular interest is the favorable outcome of FM in
association with hypermobility noted in both adults22 and schoolchildren19. The possible reason for this good outcome is improved physical function and exercise activity.
It is well known that symptoms of FM may wax and wane and adherence to rigid ACR criteria for FM diagnosis, particularly with regard to the tender point count, might in fact be somewhat
artificial. The authors in the reported study have shown that there is an association of hypermobility and FM-like syndrome although the strict criteria for FM were not completely fulfilled in 32 out
of 88 patients1. All patients in the reported study group experienced widespread pain, with 16% observed to be hypermobile. This figure represents more than double the rate of hypermobility noted in
the controls. The results of this study support the association of widespread pain and hypermobility in women, with some patients fulfilling ACR criteria regarding tender point count2.
There is thus increasing evidence that at least a subgroup of patients with soft tissue MSK pain, widespread pain, or FM are hypermobile. Clearly, hypermobility is not the only or the major factor
in the development of widespread pain or FM, but rather a contributing mechanism in some individuals. Physical conditioning and regular but not excessive exercise is probably protective towards the
development of MSK pain. Further study should be directed towards understanding exercise and physical activity of hypermobile individuals with and without MSK pain. It thus seems reasonable to
hypothesize that repeated minor traumatic episodes may be experienced by hypermobile individuals who are somewhat physically deconditioned, with resulting MSK pain that may eventually amplify into a
more diffuse pain syndrome recognizable as FM.
MARY-ANN FITZCHARLES, MB, ChB, MRCP(UK), FRCPC,
Associate Professor of Medicine,
Division of Rheumatology,
McGill University,
Montreal General Hospital,
1650 Cedar Avenue,
Montreal, QC H3G 1A4, Canada;
E-mail: mary-ann.fitzcharles@muhc.mcgill.ca
Address reprint requests to Dr. Fitzcharles.
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