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May 27, 2008

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Musculoskeletal disorders in health and safety

Are traditional approaches aimed at combating musculoskeletal disorders too limited in their scope? Andrew Baird believes so, and argues for a move away from a simplistic ergonomics method to a more sophisticated bio-psychosocial model.

Emotive language is often used to describe the rising incidence of musculoskeletal disorders. Even the director-general of the World Health Organisation has suggested that back pain has reached “epidemic” proportions, while Gordon Waddell, author of The back pain revolution, has described back pain as “a 20th-century medical disaster”.1

If that weren’t enough, the costs are absolutely staggering, with some estimates putting this figure at close to 2 per cent of gross domestic product. To put this into some kind of medical perspective, MSDs have a societal cost greater than that of cancer, heart disease and AIDS combined! It’s no wonder there is a clamour to ‘do something about it’. But before we get too carried away, it may be wise to consider exactly what the latest medical and scientific knowledge is telling us.

When we talk about MSDs, for many people the first thought would be of a specific injury, such as tennis elbow, or a prolapsed disc. However, such conditions are nowhere near as prevalent as one might think. It has been recognised for some time that while most people will experience back pain at some point in their lives, only about 15 per cent will be given a positive diagnosis. The picture for upper-limb problems would appear to be similar, with only about 20 per cent fitting a specific diagnosis. The majority of problems we come across are ‘non-specific’ or ‘idiopathic’ (of unknown origin).

Given that we’re often unsure which tissue, if any, is the source of an individual’s discomfort, it is no great surprise that these conditions are difficult to treat. Many safety professionals will have seen headlines suggesting that physiotherapy doesn’t work, manipulation doesn’t work, and, while acupuncture may help, it doesn’t seem to matter where you stick the needles!2 In its guidance on manual-handling legislation,3 the HSE states that “modern medical and scientific knowledge stresses the importance of an ergonomics approach to remove or reduce the risk of manual-handling injury”, but the effectiveness of ergonomics interventions has also been questioned.

There is an old physio ‘in-joke’, which runs: “Most back pain will resolve itself within a month, but if you go and see a physio, it will only take four weeks!” That is not meant as an attack on physiotherapists, who have an important role to play in the management of these conditions, but it reflects the fact that most of these common conditions will get better almost regardless of any intervention.

Pathology paradox

Even when we can identify particular tissue damage, we are left with a ‘pathology paradox’ when it comes to symptoms – the amount of pain and the amount of any damage are not clearly related. One of the problems with conditions like back pain is that there is little to see without the aid of expensive imaging systems, such as MRI scans. But even if we look at a condition, such as osteoarthritis, where a sufferer can experience quite obvious joint deterioration, we see no clear link between deterioration and symptoms.4

What’s more, around 40 per cent of those with quite profound deterioration report no symptoms at all. This has led the clinical and rehabilitation communities to retract from simple ‘biomedical’ models to tackle MSDs.

With that in mind, we can return to the issue of costs. While certainly staggering, costs are by no means evenly distributed. In fact, the vast majority of the cost (perhaps as much as 90 per cent) is associated with fewer than 10 per cent of cases.5 These ‘problem’ cases are the individuals who fail to recover.

Typically, people in this group do not suffer any greater objective ‘abnormality’ than their counterparts who do recover, but they are left with problematic symptoms that lead to absence, place demands on health-care resources, and, ultimately, result in disability.

Also relating to this ‘problematic minority’, HSE figures suggest that, while we may be seeing a reduction in numbers affected, average days lost per case have increased. Tackling the total number of days lost from injury and illness is an EU priority, but whether we take an economic view (absence, drain on health-care resources, etc.) or a ‘moral’ standpoint (quality of life, pain and suffering, etc.) we can see that the main focus should be on the ‘problematic minority’.

Understanding pain

Individuals in the ‘problem minority’ group do not have a musculoskeletal problem so much as a chronic pain problem. Pain was once considered simply a symptom, but increasingly we see chronic pain as a ‘disease’ in its own right. Indeed, the International Association for the Study of Pain (IASP) defines pain as: “An unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage.”

All pain has both sensory and emotional components – so, if we are to address pain, we must deal with both aspects. While acute (short-term) pain is primarily a sensory experience (nociception), chronic (long-term) pain is a much more ‘emotional’ experience. This may seem at odds with our basic beliefs, but it is implicitly familiar to us. We have all witnessed the child who falls over and looks around before reacting – if no one appears concerned, the child may well dust themselves off and carry on playing. On the other hand, if those looking on act with alarm and rush to the child, the chances are the child will cry. This is an example of thoughts and emotions impacting on acute pain.

I undertook some research that looked at the attitudes of workplace ‘influencers’ to chronic back pain (including back-care advisors, occupational health, health and safety, human resources, and associated consultants).6 It was interesting to note that many of those who took part in the study mentioned complicating factors, such as psychological issues or financial pressures, when trying to get someone back to work.

If we consider our ‘problematic minority’ with chronic pain, the best predictors of continued pain and related care-seeking behaviour are not objective clinical findings, such as scan results, but rather the ‘psychosocial’ factors and mental-health issues, such as anxiety and depression.

The mention of mental-health issues can often lead to problems. Sometimes people question whether the pain is ‘real’, and sufferers can become very defensive. In reality, all pain is ‘in the head’ – in the sense that it has no meaning outside of the brain. The areas of the brain that are active in pain all have other functions, and can be described as ‘emotional centres’. It should come as no surprise then that pain affects mood, and vice-versa.

Since the mid-1960s, when Melzack & Wall introduced the Gate Control Theory,7 we have recognised that the brain can influence the signals it receives in relation to pain. According to their model, signals from the brain can open or shut a ‘pain gate’, thereby amplifying or inhibiting the signal travelling up to the brain. This can explain why those with serious injuries sometimes report no pain, but can also explain hypersensitivity to apparently innocuous stimuli. Individuals on rehabilitation programmes are taught about ‘the gate’, and the techniques they can use to control it.

Recent advances in brain-scanning technologies have further improved our understanding of pain, and studies have shown that hypnotising someone to believe they are in pain can elicit essentially the same brain activity as a noxious stimulus.8 This shows that we need no signals from the periphery to generate a ‘real’ pain response. It therefore makes no sense to assume that pain isn’t real and that an individual is malingering, simply because we have been unable to identify specific tissue damage.

Traditional approaches

Interventions in the past have tended to see MSDs as a biomechanical problem, based on the idea that if we overload tissues they will fail. This kind of ‘engineering’ approach would suggest that MSDs are amenable to primary prevention and that if we control the physical risks, then we should control the problem. It can clearly be seen in the HSE’s original HSG60 Work-related upper-limb disorders – a guide to prevention, published in 1990 (see diagram below).

Evidence does show that force, posture and repetition (particularly in combination) can indeed impact upon MSDs, yet it falls some way short of explaining the presentation of MSDs that are seen in the workplace. Some would even argue that these simplistic explanations have left the discipline of ergonomics open to criticism. Edward Huskisson suggested that: “[F]or ergonomists, RSI was the answer to a maiden’s prayer. They multiplied and measured, taking an inch off the height of the desk and adding a centimetre to the width of the backrest. But did it help? Most commentators have concluded that it didn’t.”9

This was a rather dismissive statement and unsupported by solid evidence, but he had a point. Indeed, a later review by Szabo & King was positive about the contribution of ergonomics to improvements in workplace comfort, but suggested that: “[M]any proponents of ergonomics assert that the elimination of certain risk factors related to force, repetition, and posture can prevent, or even cure work-related musculoskeletal disorders of the upper extremity. However, there is little scientific support for this position.”10 It is notable, too, that the recent HSE research report, Management of upper-limb disorders and the biopsychosocial model, echoes this view.11

The explanation that sits most comfortably within a traditional biomechanical view is that psychosocial factors influence physical exposure – muscle tension leads to tissue loading and behavioural changes, such as skipping breaks, which all add to the duration of exposure. This may be true, but there is also a wealth of evidence that shows that psychosocial factors have a direct influence on the symptoms themselves.

A broader approach

Unfortunately, the term ‘psychosocial factors’ is rather ill-defined, and has become the subject of heated debate within the ergonomics community. The HSE’s revised HSG60, released in 2002, was influential in that it made the consideration of psychosocial factors explicit, and provided a list of issues to consider.12 However, the list only covered issues related to the task and organisation, and ignored the highly influential individual factors routinely cited in the clinical and rehabilitation literature.

Studies have shown that organisational factors, such as lack of supervisor support, can have an impact on a par with highly repetitive work. But individual factors, such as beliefs about pain and fear, are likely to be even more significant. In fact, evidence shows that fear of pain is more disabling than the pain itself. Early access to a physiotherapist can be particularly beneficial in this regard, as they are perfectly placed to rule out serious conditions, allay fears, prescribe appropriate exercises, and keep people at work.


It is essential that we move away from simple biomechanical models to deal with MSDs. Instead, we need to adopt a bio-psychosocial method. This new thinking should embrace the following elements:

• A primary aim of MSD management systems must be the avoidance of ‘chronicity’ – this not only directly addresses the issue of ‘lost days’ but also key quality-of-life indicators;

• Those working with MSDs must have an understanding of pain, so that they can fully appreciate the impact of psychosocial factors;

• MSD management systems cannot rely solely on primary prevention – while workplace factors are important, other individual and non-work factors will have as big an impact and cannot be controlled by traditional risk-based approaches.

Pain should be discussed from biomechanical, neurological, psychological and socio-cultural perspectives, all of which impact upon MSDs. That is not to deny the importance of the ‘usual suspects’, such as anatomy and biomechanics, but by putting pain first it is much easier to see how psychosocial factors impact upon MSDs and, by extension, to understand the presentation of symptoms evident in today’s workplaces. Such an approach may seem more complicated than simple biomechanical models, but as a wise soul once said: “There’s a simple answer to everything, and it’s always wrong!”


1 Waddell, G (2004): The Back Pain Revolution (2nd Edition), (Churchill Livingstone), p2

2 Haake, M et al (2007): ‘German acupuncture trials (GERAC) for chronic low-back pain randomised – multicenter, blinded, parallel-group trial with three groups’, Arch Intern Med. 167(17): 1892-1898

3 HSE (1998): Manual Handling Operations Regulations 1992 – Guidance on Regulations (L23), HSE Books, p3

4 Kidd, B L (2006): Osteoarthritis and joint pain’, Pain 123, 6–9

5 Verbunt, J A (2003): ‘Disuse and deconditioning in chronic low-back pain: Concepts and hypotheses on contributing mechanisms’, Eur J Pain, 7(1), 9-21

6 Baird, A, Haslam, R and Haslam, C (2006): ‘Life, lifting and luck – a qualitative analysis of attitudes towards back pain at work’, in Proceedings of the 16th World Congress of the International Ergonomics Association (Elsevier Science)

7 Melzack, R and Wall, P (1965): ‘Pain mechanisms: a new theory’, Science, 150, 971-979

8 Derbyshire, S et al (2004): ‘Cerebral activation during hypnotically induced and imagined pain’, NeuroImage, 23, 392– 401

9 Huskisson, E (1992): RSI – The keyboard disease, Charterhouse Conf & Comms

10 Szabo, R, and King, K (2000): ‘Repetitive Stress Injury: diagnosis or self-fulfilling prophecy?’, in The Journal of Bone & Joint Surgery, 82:1314-1322


12 HSE (2002): Upper-limb disorders in the workplace, HSG60 (rev), ISBN 0 7176 1978 8

The author delivered a talk on this subject at the Ergonomics Society’s conference, which took place in April;

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