Despite worldwide attention for more than four decades, musculoskeletal disorders (MSDs) remain a substantial concern at work and result in considerable personal and societal burden. This slow progress is not for want of trying. Prevention of MSDs has been emphasized in multiple jurisdictions. For example, in 2007 the European Agency for Safety and Health at Work organized a major campaign, “Lighten the Load – How to prevent Musculoskeletal Disorders (MSDs)” and the National Institute for Occupational Safety and Health (NIOSH) in the USA specifically identified MSDs as a major focus in their National Occupational Research Agenda. However, the results from surveys, published sick leave, and lost time data indicate we have a way to go in preventing MSDs. Which leaves us with a question: Why have we not solved the MSD problem?
- How well do we understand MSDs and their burdens?
- How good are our MSD risk factors?
- How effective and informative are current workplace MSD assessment approaches?
- How effective are the recommended interventions in actually reducing MSDs in the workplace?
- How intensely and widely implemented are workplace interventions to prevent MSD?
- How well are we improving disability outcomes for MSDs?
An example of how a weak link may be derailing our ability to reduce MSDs could be if we do have multiple efficacious interventions that we can recommend to workplaces, but those interventions are not widely implemented in workplaces. We would then not be effective in addressing the societal concern for MSDs. A fruitful research focus – one which could markedly improve MSD prevention – would be to address this potential “weakest link” and develop and test ways of increasing the adoption of efficacious interventions. This research focus would be clearly different than, for example, if we found that workplaces were not performing adequate risk assessments and thereby not intervening on influential risk factors.
We do need to acknowledge that our knowledge of MSDs has developed greatly over the past decades. Multiple clinical examination diagnostic systems have been developed and consensus documents have been created. Laboratory studies have shown how different tissues can be damaged by acute and extended exposures. We have good information concerning the injury mechanisms for nerve functioning during impingement and pressure applications, herniation and bony damage to spinal motion units under combinations of loading, posture and frequency. We also have an understanding of how pain is produced in muscles and muscle fibres due to long-duration, low-level static contractions, and the effects of high job strain on the hormonal and endocrine systems. The interaction of these multiple factors argues for the use of a bio-psycho-social rather than a biomedical model.
In asking the first question, how well do we understand MSDs and their burdens, I want to reflect on what knowledge gaps could be frustrating our prevention efforts. We may choose to use tissue damage, physiological function, clinical examination, pain, functional decrements, or work disability as measures of MSD burden or to define a case. Different choices could misrepresent the burden, risk factors, the effects of treatment, or the effectiveness of workplace interventions. On the other hand, if we are grouping disorders with very different etiologies under one umbrella (for example, “non-specific low back pain”), it may lead to either focusing on misleading risk factors or inappropriate interventions. For low back pain, we could ask whether it is due to cumulative damage to a structure, a loss of spine stability ; or a statistically rare loading outlier in a normally innocuous task ? Each of these three different mechanisms of injury could lead down divergent exposure and intervention paths.
Similarly, we now have a substantial and consistent body of knowledge that demonstrates the strong association of MSDs with many exposures found in workplaces and have high attributable fractions for many of these. Exposure measures have improved over the years from initially just considering job titles, to self-reports of physical and psychosocial risk factors, to structured observations, and more recently to technical measures of muscle activity or modeled joint loads. Identified risk factors now include mechanical factors (force, posture, repetition, duration), work organizational factors (worker perceptions of demand, control, and co-worker and supervisor support; the so-called psychosocial factors) as well as individual factors. These relationships have been demonstrated in multiple types of work, with a wide variety of exposure assessment approaches, and a wide variety of study designs, including high-quality prospective cohort studies; the NIOSH MSD Consortium Studies are an example of a concerted attack on this question.
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