This blog is an amended version of some text from my recent PhD that looked at the assessment and management of patellofemoral pain. As such, my work is a product of supervision and collaboration. So I would like to start by acknowledging and thanking my supervisors Pip Logan and Paul Hendrick, and collaborators Marcus Bateman, Sinead Holden, Chris Littlewood, Fiona Moffatt, Michael Rathleff, James Selfe and Toby Smith.
The first part of this blog discussed how traditional thinking often attributes improvements to pain to changes tissues structure and function. This historical model of clinical reasoning fails to consider the full biopsychosocial spectrum of factors. This model is frequently attributed to the dualistic philosophy of René Descartes (1596 – 1650) . Referred to as ‘mind-body dualism’, it was a philosophical viewpoint that separated the mind and body into two separate distinctions. The body was suggested as working like a machine, whereas the brain was considered the soul, not confirming to laws of natural science. It initiated a paradigm of medical practice through which the body was considered a machine that had ‘broken down’; Descartes describes pain as functioning “to indicate to the soul the bodily damage suffered” . However, this orientation of medical practice neglects to consider important psychosocial factors in health and illness .
Over the last half-century, knowledge surrounding pain and pain mechanisms has expanded beyond this reductionist understanding. Historically, Melzack and Wall’s (1965) gate-control model proposed that pain signals could be modulated in the spinal cord and brain, creating a feedback system . The biopsychosocial model of pain developed further in the 1980s, partly in response to Melzack and Wall’s seminal paper, but also in response to poor treatment outcomes in patients with chronic musculoskeletal conditions , and due to innovative non-harmful noxious stimuli in vivo experiments, that cast doubt about the validity of the biomedical model of pain . These experiments recorded activity in nociceptors, while simultaneously monitoring pain levels during experimentally induced pain. They demonstrated that pain did not correlate with tissue damage, and that relationships between pain and nociception was variable.
It is now understood that while nociceptors provide a physiological sensory input, pain emerges in the person as a result of a scrutiny process and we experience it in an area of the body deemed under threat , and that the severity of the pain response is not always associated with the intensity of the stimulus, but other factors including pain history and memory and psychological factors. There are now several modern models in relation to pain perception and nociception, including the mature organism model , the pain and movement reasoning model , and predictive processing . However, the most widely accepted is the neuromatrix model, proposed by Melzack in 2001 [8,9].
The neuromatrix model of pain proposes pain is perceived and experienced when tissue is considered to be under threat. Many inputs into the central nervous system will affect the perception of threat, with each one further influencing other inputs. This includes: nociception from the musculoskeletal system; psychosocial factors like memories, anxiety, beliefs; and affective factors such as pain behaviour. A pain experience may be triggered by sensory input from nociceptors alone, or independently from them from other inputs .
The fear-avoidance model of pain has been identified in patients , and in clinicians [11–13]. This model asserts that cognition and emotion underpin fear of pain and potential ‘tissue damage’, leading to ‘safety-seeking’ behaviours and hypervigilance; which paradoxically maintain or exacerbate the pain and disability . When researched qualitatively, within shoulder pain populations, clinicians have confessed to fear of tissue damage with pain during exercise . And, despite a lack of empirical evidence to support this view , it has been further suggested that pain with exercise could also result in increased stress responses within the brain, with subsequent increases in overall pain sensitivity .
The iatrogenic effect of healthcare, where actions of the healthcare professional negatively affect the patient, is an emerging field of research; with low back pain, knee and shoulder pain populations demonstrating this phenomenon [18–21]. My work on patellofemoral pain has shown an iatrogenic effect of reduced physical activity and exercise levels as a result of pain and activity avoidance advice from clinicians. In contrast, if pain is perceived as non-threatening by patients and clinicians, it can help patients maintain physical activity levels, which may have a positive influence on recovery [22,23].
Pain and exercise is an important factor. Advice is often given by healthcare practitioners on how to manage exacerbations of musculoskeletal pain during physical activity or exercise. This is significant when we consider that, for example, 50% of dropouts from exercise interventions for type 2 diabetes is attributable to musculoskeletal pain . Physical inactivity is one of the 10 leading risk factors for death worldwide , and an estimated $117 billion a year in healthcare costs in the US are attributable to physical inactivity . Healthcare practitioners should have the skills to encourage people, through education on interventions, with persistent musculoskeletal pain to remain as physically active as possible. This education should involve discussing that there is no evidence pain during exercise exacerbates musculoskeletal symptoms in the long-term, and there may be a short-term benefit.
This two-part blog has challenged the idea that therapeutic exercises for chronic musculoskeletal pain should be pain-free. In the current practice surveys that have examined this aspect of exercise prescription, pain-free exercise is the most common form of therapeutic exercise prescribed [12,13], and should be open to scrutiny. Traditional pain models that describe tissue pathology and biomechanics as a source of nocioceptive input, with associated pain equating to ‘harm’, have been insufficient in the management of long-term musculoskeletal pain .It seems plausible to suggest that such approaches might exacerbate fear-avoidance behaviours to the detriment of patients’ recovery and overall level of physical activity participation .In conclusion, pain may not need to be avoided during therapeutic exercises and may have some additional benefits, for example, the associated health benefits from improvements in physical activity levels [20,22,23].
 Duncan G. Mind-body dualism and the biopsychosocial model of pain: What did Descartes really say? J. Med. Philos. A Forum Bioeth. Philos. Med., vol. 25, Journal of Medicine and Philosophy Inc.; 2000, p. 485–513.
 Melzack R and Wall P. Pain mechanisms: a new theory. Science (80- ) 1965.
 Moseley GL. Reconceptualising pain according to modern pain science. Phys Ther Rev 2007;12:169–78. doi:10.1179/108331907X223010.
 Thacker M, Moseley L. Pathophysiological Mechanisms of Chronic Pain. In: Corns J, editor. Routledge Handb. Philos. Pain, Routledge; 1 edition; 2017, p. 124–39.
 Gifford LS. The mature organism model. Whiplash—Science Manag Fear, Avoid Beliefs Behav Top Issues Pain 2013;1:45–56.
 Jones LE, O’Shaughnessy DFP. The pain and movement reasoning model: introduction to a simple tool for integrated pain assessment. Man Ther 2014;19:270–6.
 Seth AK. A predictive processing theory of sensorimotor contingencies: Explaining the puzzle of perceptual presence and its absence in synesthesia. Cogn Neurosci 2014;5:97–118.
 Gatchel RJ. Clinical essentials of pain management. American Psychological Association; 2005.
 Melzack R. Pain and the neuromatrix in the brain. J Dent Educ 2001;65:1378–82.
 Chou R, Shekelle P. Will this patient develop persistent disabling low back pain? JAMA 2010;303:1295–302. doi:10.1001/jama.2010.344.
 Nijs J, Roussel N, Paul van Wilgen C, Köke A, Smeets R. Thinking beyond muscles and joints: Therapists’ and patients’ attitudes and beliefs regarding chronic musculoskeletal pain are key to applying effective treatment. Man Ther 2013;18:96–102.
 Smith BE, Hendrick P, Bateman M, Moffatt F, Rathleff MS, Selfe J, et al. Current Management Strategies for Patellofemoral Pain: An online survey of 99 practising UK physiotherapists. BMC Musculoskelet Disord 2017;18. doi:10.1186/s12891-017-1539-8.
 Littlewood C, Lowe A, Moore J. Rotator cuff disorders: a survey of current UK physiotherapy practice. Shoulder Elb 2012;4:64–71. doi:10.1111/j.1758-5740.2011.00164.x.
 Jones S, Hanchard N, Hamilton S, Rangan A. A qualitative study of patients’ perceptions and priorities when living with primary frozen shoulder. BMJ Open 2013;3:e003452.
 Littlewood C, Mawson S, May S, Walters S. Understanding the barriers and enablers to implementation of a self-managed exercise intervention: a qualitative study. Physiotherapy 2015;101:279–85.
 Smith BE, Hendrick P, Smith TO, Bateman M, Moffatt F, Rathleff MS, et al. Should exercises be painful in the management of chronic musculoskeletal pain? A systematic review and meta-analysis. Br J Sports Med 2017;51:1679–87. doi:10.1136/bjsports-2016-097383.
 Nijs J, Lluch Girbés E, Lundberg M, Malfliet A, Sterling M. Exercise therapy for chronic musculoskeletal pain: Innovation by altering pain memories. Man Ther 2015;20:216–20. doi:10.1016/j.math.2014.07.004.
 Lin IB, O’Sullivan PB, Coffin JA, Mak DB, Toussaint S, Straker LM, et al. Disabling chronic low back pain as an iatrogenic disorder: a qualitative study in Aboriginal Australians. BMJ Open 2013;3:1–8.
 Webster BS, Bauer AZ, Choi Y, Cifuentes M, Pransky GS. Iatrogenic consequences of early magnetic resonance imaging in acute, work-related, disabling low back pain. Spine (Phila Pa 1976) 2013;38:1939–46.
 Smith BE, Moffatt F, Hendrick P, Bateman M, Rathleff MS, Selfe J, et al. The experience of living with patellofemoral pain—loss, confusion and fear-avoidance: a UK qualitative study. BMJ Open 2018;8:e018624. doi:10.1136/bmjopen-2017-018624.
 Cuff A, Littlewood C. Subacromial impingement syndrome–What does this mean to and for the patient? A qualitative study. Musculoskelet Sci Pract 2018;33:24–8.
 Leeuw M, Goossens MEJB, Linton SJ, Crombez G, Boersma K, Vlaeyen JWS. The fear-avoidance model of musculoskeletal pain: current state of scientific evidence. J Behav Med 2007;30:77–94. doi:10.1007/s10865-006-9085-0.
 Vlaeyen JW, Linton SJ. Fear-avoidance and its consequences in chronic musculoskeletal pain: a state of the art. Pain 2000;85:317–32.
 Praet SFE, Van Rooij ESJ, Wijtvliet A, Boonman-de Winter LJM, Enneking T, Kuipers H, et al. Brisk walking compared with an individualised medical fitness programme for patients with type 2 diabetes: a randomised controlled trial. Diabetologia 2008;51:736–46.
 WHO. Global Health Risks: Mortality and burden of disease attributable to selected major risks. Bull World Health Organ 2009;87:646–646. doi:10.2471/BLT.09.070565.
 Carlson SA, Fulton JE, Pratt M, Yang Z, Adams EK. Inadequate physical activity and health care expenditures in the United States. Prog Cardiovasc Dis 2015;57:315–23. doi:10.1016/j.pcad.2014.08.002.