Abstract
Multisite musculoskeletal pain is common among people suffering from low back pain. Although the mechanisms behind co-occurrence of multiple somatic symptoms and musculoskeletal pain are still unknown, patients with co-morbidities and co-occurring musculoskeletal symptoms tend to have worse functional status, a poorer prognosis and respond less favourably to treatment. Evidence also suggests that the more pain sites a patient reports, the more reduced their physical and mental function will be regardless of location of pain. At the same time, evidence suggests that strategies for diagnosis and treatment of low back pain and other musculoskeletal disorders such as neck pain and lower limb osteoarthritis are very similar. In this chapter, we discuss the prevalence, consequences, and implications of commonalities between low back pain, pain in other sites and co-occurring pain. In addition, we propose a conceptual framework for a common stepwise approach to the diagnosis and management of back and musculoskeletal pain.
Pain is a common experience in anyone’s life, and individual episodes of pain will quickly resolve in most cases. Chronic musculoskeletal pain however, which affects over 20% of the adult population , is the most common cause of severe, long-term, physical disability and a substantial burden to both individuals and societies . Recently published data from the National Health and Wellness Survey and based on interviews of 53,524 people across the UK, France, Spain, Germany and Italy suggest that 9% of the general population suffers from moderate-to-severe daily somatic pain most commonly located in the back, translating into almost 50 million people in these five countries experiencing daily pain . The authors found that the presence of severe, daily pain increased both the number of visits to health-care providers and emergency departments by more than 100%, as well as the number of hospitalisations by more than 250% . In addition, people with severe daily pain were less likely to be in full-time employment and reported substantially higher rates of both absenteeism (i.e., being absent from work) and presenteeism (i.e., being present at work but working at reduced capacity) when compared to those reporting no pain . Arguably the most prevalent musculoskeletal pain disorder, low back pain (LBP), has been highlighted as the leading cause of disability affecting approximately 632 million people worldwide . However, LBP rarely occurs on its own, and there is increasing evidence showing that patients who seek health care with an episode of LBP consistently report co-morbidities in other body systems and co-occurrence of multisite musculoskeletal pain as well .
Also noteworthy is the fact that recent evidence suggests the diagnosis and management of the most prevalent musculoskeletal painful conditions such as low back and neck pain, lower limb osteoarthritis (OA), fibromyalgia and widespread pain present many commonalities. For instance, regardless of the site of pain, the diagnosis of many musculoskeletal painful conditions relies largely on the assessment of clinical signs and symptoms and clinical management guidelines across these conditions generally focus on remaining active and at work. Self-management, maintaining levels of physical activity and exercise along with advice regarding appropriate pain relief appear to be an overriding principle, with therapist-delivered interventions such as manual treatment and acupuncture recommended for selected patients only, whereas multidisciplinary pain management programmes and surgery are recommended only for very few . This brings a different and commonly ignored perspective to the diagnosis and management of LBP, as both research and clinical guidelines tend to focus on single pain sites such as the back, neck, knee or hip instead of addressing musculoskeletal pain and disability in general. This chapter will focus on the commonalities between LBP, and other – often co-occurring – musculoskeletal pain, and will propose a common stepwise approach to the diagnosis and management of these conditions.
How common is co-occurring musculoskeletal pain and what are the patterns?
In health care, we increasingly manage individuals with multiple co-existing diseases and symptoms – in fact, this is the norm rather than the exception . Therefore, despite the common belief that regional musculoskeletal pain such as back, neck, hip or knee pain are isolated clinical entities, research has provided compelling evidence that individuals rarely report pain in only one body site . For instance, Kamaleri et al. found that 17% of a Norwegian population-based sample reported pain in more than five body sites during the past week, with 39% reporting having experienced multisite pain in the past year as well . Hartvigsen et al. also found that in the adult Danish population, 40% experience pain in at least one site, additional to the identified primary musculoskeletal pain site during the past 2 weeks . LBP has consistently been reported to be the most common pain site whether defined as one site among several or as the primary site of pain . The pattern and number of pain sites appear to be a stable phenomenon over time as Kamaleri et al. found little change in the number of painful sites over 14 years both at the population and at the individual level. In fact, 46% of participants reported the same number plus or minus one pain site at baseline and 14 years later . This is of course disturbing as we know LBP, as well as other musculoskeletal pain such as neck and knee pain, start at an early age and thus may predetermine an individual to a lifelong trajectory of pain (see chapter on life course of low back pain in this issue (Ref. )).
Whether the common experience of pain in multiple body sites follows a certain pattern or whether pain sites occur together in a random pattern is not known. Hartvigsen et al., using latent class analysis of primary pain-site reports, found that when a person reported primary pain in the spine, that is, neck, mid back or low back, there was a greater likelihood of co-occurring pain elsewhere in the spine whereas when the person reported primary pain in the extremities, there was a greater likelihood of co-occurring pain elsewhere in that extremity . Likewise, Coggon et al. reported that, among 12,410 workers from 18 countries, those who reported having musculoskeletal pain at a specific site were twice as likely to report pain at another anatomical site compared to workers without pain at this site, and that this co-occurring pain was most often located at adjacent sites and corresponding bilateral sites . Schmidt and Baumeister, also using latent class analysis in a population-based sample, reported that simply counting the number of pain sites, irrespective of their spatial patterns, provided a meaningful pain classification, which was predictive of social functioning . Thus, although having pain in one body site greatly increases the chance of also experiencing pain in other parts of the body, it is still unclear whether co-occurring musculoskeletal pain should be classified according to spatial patterns or number of anatomical sites.
What are the consequences of having pain in more than one site?
Regional pain such as pain in the back is more severe and disabling if pain is also present in other body regions and there is consistent evidence that having multisite pain is associated with decreased functioning and worse prognosis when compared to having pain in one site only. In fact, there appears to be an almost linear association between number of pain sites and reduced function in terms of physical fitness, daily activities and social activities, as well as worse mood ( Fig. 1 ). Furthermore, the risk of an episode of pain in the lower back becoming chronic increases sixfold if the person is also suffering from pain at other sites in addition to the back ; and having pain in the upper body alongside having pain in the lower back nearly quadruples the risk of poor outcome 1 year later among primary-care, LBP patients . When compared to persons without pain, Norwegians referred to an LBP clinic had a higher prevalence of many other symptoms including pain in the feet during exercise, headaches and migraines, sleep problems, anxiety and depression . When compared to persons with LBP only, Norwegians reporting pain in other sites alongside their LBP had longer duration of pain, higher pain intensity, lower self-rated health, more sleep disturbances and higher body mass index . These patterns are not only observed in back-and-neck-pain patients. Pain in the lower extremity for instance is also more severe and disabling if pain is present at other sites at the same time and an increasing number of pain sites generally increases the risk of worse future outcomes and current poor overall function, poor fitness and negative emotions. This will result in both reduced daily physical and social activities . Office workers suffering from neck pain have greater pain intensity if they also have pain in other body parts . The same is true for knee pain, where the presence of pain in other areas such as the foot, low back or elbow negatively affects scores for knee pain and disability . Thus, apparently regardless of pain location, persons experiencing pain in more than one anatomical site consistently experience greater impact on daily function and quality of life and greater risk of a poor prognosis including, in general, poorer response to treatment.
What are the consequences of having pain in more than one site?
Regional pain such as pain in the back is more severe and disabling if pain is also present in other body regions and there is consistent evidence that having multisite pain is associated with decreased functioning and worse prognosis when compared to having pain in one site only. In fact, there appears to be an almost linear association between number of pain sites and reduced function in terms of physical fitness, daily activities and social activities, as well as worse mood ( Fig. 1 ). Furthermore, the risk of an episode of pain in the lower back becoming chronic increases sixfold if the person is also suffering from pain at other sites in addition to the back ; and having pain in the upper body alongside having pain in the lower back nearly quadruples the risk of poor outcome 1 year later among primary-care, LBP patients . When compared to persons without pain, Norwegians referred to an LBP clinic had a higher prevalence of many other symptoms including pain in the feet during exercise, headaches and migraines, sleep problems, anxiety and depression . When compared to persons with LBP only, Norwegians reporting pain in other sites alongside their LBP had longer duration of pain, higher pain intensity, lower self-rated health, more sleep disturbances and higher body mass index . These patterns are not only observed in back-and-neck-pain patients. Pain in the lower extremity for instance is also more severe and disabling if pain is present at other sites at the same time and an increasing number of pain sites generally increases the risk of worse future outcomes and current poor overall function, poor fitness and negative emotions. This will result in both reduced daily physical and social activities . Office workers suffering from neck pain have greater pain intensity if they also have pain in other body parts . The same is true for knee pain, where the presence of pain in other areas such as the foot, low back or elbow negatively affects scores for knee pain and disability . Thus, apparently regardless of pain location, persons experiencing pain in more than one anatomical site consistently experience greater impact on daily function and quality of life and greater risk of a poor prognosis including, in general, poorer response to treatment.
Why do so many have more than just a pain in the back?
The way multisite musculoskeletal pain develops is not known, even though different theories have been proposed . A traditional biomechanical approach to back and musculoskeletal pain would suggest that pain in the absence of trauma, pathology or infection occurs in a body region because of injury, overload or biomechanical abnormalities . Consequently, prevention, diagnosis and treatment of pain would largely be dependent on the site of pain and generally be specific for that site. If indeed pain tends to occur at adjacent sites in a predictable pattern such as previously suggested , this would to some degree support a biomechanical hypothesis for an underlying cause whereas a more unpredictable or even random pattern of pain might be better explained by other mechanisms. The fact that widespread pain is much more common than can be expected by chance alone and that there is an additive negative effect of number of pain sites suggests that the injury/overload model is neither sufficient in explaining LBP or musculoskeletal pain at other sites, nor sufficient in its diagnosis and management . Central nervous system centralisation to pain is one plausible explanation, and recent evidence suggests that not only does the presence of chronic pain in one site result in pain hypersensitivity and increased vulnerability to more widespread pain . Positron emission tomography (PET) and magnetic resonance imaging (MRI) studies indicate that chronic pain may even alter brain morphology and affect brain functions such as decision making and emotions . Another explanation is cognitive activation of stress where psychological and physiological mechanisms interact to produce pain with substantial impact on physical and psychological functioning . Prolonged psychological stress may affect sensory processing of pain and predispose to widespread musculoskeletal pain . Finally, LBP is strongly influenced by genetic components , which have been found to be more influential in more chronic and disabling LBP than for acute and less disabling LBP . Interaction between genetic and environmental factors may also explain a genetically based underlying vulnerability for chronification of pain in multiple sites , even though the specific underlying mechanisms between genes, environmental exposures and musculoskeletal pain are not yet known . In summary, recent evidence suggests that a biomechanical approach to explaining co-occurring musculoskeletal pain is insufficient. Rather, central nervous system sensitisation and possibly other factors such as behavioural and psychological mechanisms play important roles. These are likely to be strongly influenced by underlying genetic factors even though the specific mechanisms for this are not currently known.
A conceptual framework for a common approach to diagnosis and treatment
Because pain from the back and other musculoskeletal pain share many common characteristics across pain sites and because they commonly appear together, approaches to diagnosis and management may be combined in a conceptual framework regardless of site and pain distribution. We argue for a stepwise progression starting with the least intensive and least costly and then gradually progressing to more intense and costly diagnostic procedures and treatment ( Figs. 2 and 3 ). The individual components of the conceptual models are supported by recent evidence as demonstrated below, but the effectiveness and cost-effectiveness of the models, if implemented, have not been the subject of investigation. In addition, indicators for transition from one line of diagnosis and treatment to another need to be established. Nevertheless, it is our opinion that pursuing a conceptually common approach to diagnosis and treatment across musculoskeletal pain sites and distributions is rooted in current evidence and could be fruitful in a public-health- and primary-care perspective.
Implications for diagnosis in back and musculoskeletal pain
At present, the diagnosis of most painful musculoskeletal conditions such as back and neck pain, lower limb OA, fibromyalgia and chronic widespread pain in general relies largely on the assessment of signs and symptoms with limited information on the underlying pathophysiological causes . Therefore, the term ‘diagnosis’ may be better defined as a multifactorial assessment of the pain problem aiming to identify patients with high impact of pain, and at high risk of poor outcome. As a model, a stepwise diagnostic approach across musculoskeletal pain conditions may apply ( Fig. 2 ). ‘First-line diagnosis’ applies to all patients and is based on patient-reported information that includes assessment of several dimensions of the individual’s clinical pain covering both physical aspects (distribution, severity, intensity, temporal characteristics, co-morbidities and co-occurring symptoms), psychological (fear of movement, catastrophising, distress, mood and depression) and social aspects (domestic and work situation). This initial diagnosis and triage could possibly be delivered over the telephone by a trained health-care worker or clinician, which may be sufficient in some cases , or through brief encounters with primary care physicians. ‘Second-line diagnosis’ applies to patients who report ongoing and/or worsening of pain or report physical, psychological or social information that warrants closer attention. Such a diagnosis would include a consultation with a specially trained clinician and should consist of a clinical examination of the painful area and other pain sites using inspection, palpation, functional orthopaedic and neurological testing as well as a thorough assessment of physical functional capacity, emotional distress, somaticising behaviour, coping strategies and social factors using validated instruments. Second-line diagnosis would probably not always fit with routine primary care but would require consultation with health-care persons with extensive training in musculoskeletal assessment and diagnosis . ‘Third-line diagnosis’ applies to patients where there is suspicion of severe psychosocial problems, serious pathology or where surgery or aggressive pharmacological therapy should be considered. It would involve in-depth psychological and social assessment, laboratory tests and/or imaging and, in some cases, biopsies as indicated. The goals of this staged approach is to triage and stratify patients into streams of care appropriate for their symptomatology, psychological state and their social situation, which have all been strongly associated with worse prognosis of musculoskeletal pain . Imaging such as X-ray or MRI is extremely common in LBP and musculoskeletal pain; however, imaging results provide limited diagnostic value in most patients , adds cost and may even lead to unnecessary procedures and iatrogenic problems and should therefore be reserved for the small group for which it is indicated.
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