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Last year marked the 80th anniversary of the first report of an association between hypermobility and articular manifestations by Finkelstein1 and this year the 30th anniversary since the definitive description of the hypermobility syndrome (HMS) by Kirk, et al.2 In the years since these landmark publications much has been written about hypermobility and reports can broadly be categorised as those dealing with its epidemiology, measurement, clinical associations, and the mechanisms causing them. Despite this our understanding of the role of hypermobility in articular and extra-articular manifestations remains confused. Agreement on a standard method of measurement has yet to be reached and proposed associations continue to be debated. It is perhaps timely to review the current status in the light of the conflicting reports, to highlight the importance of consistency in measurement and methodology so that valid comparisons can be made between studies, and to speculate on new developments that may play a part in unravelling the confusion that presently exists.
Investigation of the clinical relevance of hypermobility has to take into account that it can be generalised2 3 or localised,4-7 genetically determined8 or acquired.9 10 It is also influenced by age,3 4 7 11-13 sex,3 12-16 and ethnicity,3 5 6 14 and some diseases such as acromegaly, hyperparathyroidism, and rheumatic fever are thought to predispose to joint laxity.9 While the majority of hypermobile people suffer no ill effects5 8 some will develop features of HMS. In young children hypermobility is so common as to be of little predictive value in determining who will develop HMS.17Mobility decreases with age and introduces the problem of defining cut off points for different age groups. There are pronounced ethnic differences in the frequency of hypermobility3 5 6 14and localised hypermobility in some populations is so common as to render it of doubtful clinical value in those populations.6 Localised hypermobility may be acquired through occupational, sporting or repetitive activities causing symptoms at specific sites. It may also result from ligamentous or capsular laxity or from joint destruction in diseases such as rheumatoid arthritis.
There is no single diagnostic test for hypermobility and because articular mobility is a graded phenomenon3 it has no precise cut off point. Interobserver bias in measurement and the use of different scoring methods3 15 18 in studies introduce difficulties in comparing data. Beighton’s modification3 of the Carter and Wilkinson method18 incorporates nine genetically determined sites one of which, forward flexion, can also be acquired through training.10 It uses an arbitrary score of four or more as a cut off for hypermobility and is quick and easy to perform. It remains the most commonly used in clinical and epidemiological studies. Of significance as to its value is that it has been included in the new proposed criteria for HMS.19 Bulbena’s method15 includes the shoulder, patella, and ankle, which are common sites of pain and it confers an advantage over Beighton’s method in the assessment of the individual patient. Mechanical devices such as the Leeds finger hyperextensometer20 provide a precise measurement of laxity at a single joint. It is hoped that the prediction that Beighton’s criteria will continue to be the standard for the foreseeable future will prove to be correct.6
New diagnostic criteria for HMS incorporating several extra-articular features have been proposed by Mishra et al. 19The aims were to improve on existing criteria, to define people with hypermobility confined to a single joint, and to assist in future genetic and molecular studies (table 1). Despite concerns about the reliance on a large number of minor criteria, subsequent application of the earlier draft criteria yielded a 93% sensitivity and a 93% specificity.21 Refinements to the criteria have since been made.19 Their value has as yet to be confirmed.
A source of great confusion in hypermobility is the conflicting reports on its clinical associations. The addition of several articular and extra-articular associations to HMS since its original description has been the subject of much debate as to which can justifiably be blamed on hypermobility. Reasons for the inconsistencies in findings are lack of uniformity and weakness in methodologies used. Many reports are based on circumstantial evidence, small numbers, and uncontrolled cross sectional studies. Lack of precise definition of the manifestation/s under investigation, no standard method for measuring articular mobility, and no agreed cut off point for hypermobility further contribute to the inconsistencies in reporting. The debate will continue until these have been issues have been settled.
Fifty years down the track there is still no agreement on the important issue of the role of hypermobility in osteoarthritis (OA), in particular whether it predisposes to premature OA.2 7 11 16 22 The mechanisms whereby OA may occur in hypermobility are either that both conditions share the same defects in connective tissue synthesis or that the risk of damage to joints through major or minor repetitive trauma is increased by hypermobility, or both. Studies that do show an association are based on circumstantial evidence and are cross sectional. Substantiation is needed in long term prospective controlled studies with clearly defined clinical and radiological criteria for OA, documentation of mobility score, hypermobility at individual sites, and the age at onset. This will determine not only whether generalised hypermobility predisposes to premature OA, either localised or generalised, but also whether localised OA develops at hypermobile sites only. If it can be conclusively shown that hypermobility is a predisposing factor to premature OA, measures to reduce the risk can be instituted.
Reports on the role of hypermobility and musculoskeletal complaints in pre-adolescents are conflicting17 23 and there is little in the way of epidemiological data available. In common with OA, longitudinal studies are needed in children to record articular mobility from an early age and to specify the exact nature of musculoskeletal symptoms that may develop. Reliance cannot be placed on historical evidence of inflammatory arthritis; it needs to be recorded clinically. Until this is resolved, causes of joint and other musculoskeletal manifestations in children should be investigated along the usual lines and hypermobility as the cause diagnosed by exclusion. In adults there is little to suggest an association between hypermobility and inflammatory arthritis.7
Matched controlled studies of sufficient numbers to allow for meaningful statistical analysis are essential to avoid either perpetuating existing unconfirmed associations or introducing claims of new associations without adequate evidence. A clinical association between systemic lupus erythematosus and hypermobility was recently proposed in an uncontrolled study,16 this despite no association being found in an earlier matched controlled study of 90 subjects many of whom had severe disease requiring long term corticosteroid treatment.24 Whether rheumatoid arthritis is linked to generalised hypermobility also deserves some comment. Established rheumatoid arthritis may preclude measurement of articular mobility because of hand, elbow, and knee involvement and in the absence of prospective studies the mobility status before its development cannot be known.
There is general agreement that soft tissue rheumatism and predisposition to injury are common associations of hypermobility. Recent studies in children23 and adults7suggest that hypermobility may play a part in the pathogenesis of fibromyalgia. If confirmed then fibromyalgia would become an additional manifestation of HMS and exercise programmes to reduce hyperextension of joint capsules and other soft tissues may reduce the severity of pain and the impact it has on quality of life.
Several extra-articular manifestations attributed to hypermobility5 9 14 have led to the suggestion that HMS may be a forme fruste of one of the well defined hereditary disorders such as Ehlers-Danlos syndrome, Marfan’s syndrome, and osteogenesis imperfecta. It remains to be seen which extra-articular manifestations presently included in HMS will be retained. Mitral valve prolapse, previously considered to be a feature of hypermobility,9 25-27 is a case in point. No difference in its incidence in hypermobile subjects compared with normal age matched controls was found when using modern echocardiographic techniques and stricter diagnostic criteria.19
Ballet and hypermobility have also produced controversy as to the possible advantage it confers.5 It has been shown that there is no advantage to being hypermobile even at professional dance level and that the risk of injury is significantly higher.28
It is hoped that before the 60th anniversary of HMS the role of hypermobility in the pathogenesis of the manifestations presently included in HMS such as premature OA will have been resolved. Until then the routine screening29 of people for hypermobility, apart from being impractical, cannot be justified. For the present, screening for hypermobility might be appropriate for people embarking on occupations or recreations demanding high levels of physical activity.
Routine assessment for hypermobility on the other hand should be included as part of the clinical examination of all patients attending rheumatology clinics as a substantial number will have HMS. Many of the manifestations are mild and self limiting and the patient can be reassured as to prognosis and unnecessary investigation and inappropriate treatment can be avoided.
There have been important advances in the understanding of the genetic and molecular aspects of collagen in the hereditary connective tissue disorders.30 Application of the techniques used in those disorders to HMS has only recently begun. To what extent these studies will influence our understanding of HMS remains to be seen.
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