Original article Mechanisms-based classifications of musculoskeletal pain: Part 3 of 3: Symptoms and signs of nociceptive pain in patients with low back (leg) pain Keith M. Smart a, * , Catherine Blake b , Anthony Staines c , Mick Thacker d, e , Catherine Doody b a Physiotherapy Department, St Vincent’s University Hospital, Elm Park, Dublin 4, Ireland b UCD School of Public Health, Physiotherapy and Population Science, University College Dublin, Belfield, Dublin 4, Ireland c Health Systems Research, School of Nursing, Dublin City University, Dublin 9, Ireland d Centre of Human and Aerospace Physiological Sciences, Kings College London, London, United Kingdom e Centre for Neuroimaging Sciences, Institute of Psychiatry, Kings College London, London, United Kingdom article info Article history: Received 14 September 2011 Received in revised form 9 January 2012 Accepted 1 March 2012 Keywords: Nociceptive pain Pain mechanisms Classification Low back pain abstract As a mechanisms-based classification of pain ‘nociceptive pain’ (NP) refers to pain attributable to the activation of the peripheral receptive terminals of primary afferent neurones in response to noxious chemical, mechanical or thermal stimuli. The symptoms and signs associated with clinical classifications of NP have not been extensively studied. The purpose of this study was to identify symptoms and signs associated with a clinical classification of NP in patients with low back (leg) pain. Using a cross-sectional, between-subjects design; four hundred and sixty-four patients with low back (leg) pain were assessed using a standardised assessment protocol after which their pain was assigned a mechanisms-based classification based on experienced clinical judgement. Clinicians then completed a clinical criteria checklist indicating the presence/absence of various symptoms and signs. A regression analysis identified a cluster of seven clinical criteria predictive of NP, including: ‘Pain localised to the area of injury/dysfunction’, ‘Clear, proportionate mechanical/anatomical nature to aggra- vating and easing factors’, ‘Usually intermittent and sharp with movement/mechanical provocation; may be a more constant dull ache or throb at rest’, and the absence of ‘Pain in association with other dysesthesias’, ‘Night pain/disturbed sleep’, ‘Antalgic postures/movement patterns’ and ‘Pain variously described as burning, shooting, sharp or electric-shock-like’. This cluster was found to have high levels of classification accuracy (sensitivity 90.9%, 95% CI: 86.6e94.1; specificity 91.0%, 95% CI: 86.1e94.6). Pattern recognition of this empirically-derived cluster of symptoms and signs may help clinicians identify an assumed dominance of NP mechanisms in patients with low back pain disorders. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction As a mechanisms-based classification of pain, where pain is classified according to the dominant neurophysiological mecha- nisms responsible for its generation and/or maintenance (Portenoy, 1989; Woolf et al., 1998) nociceptive pain (NP) has been proposed as a category of pain distinct, but not inseparable, from other mechanisms-based classifications of pain, such as ‘peripheral neuropathic’ pain (PNP) and ‘central sensitisation’ pain (CSP) (Gifford, 1998; Smart et al., 2008). Nociceptive pain refers to pain conditions assumed to be predominantly driven by the activation of peripheral nociceptive sensory fibres (Scholz and Woolf, 2002). Specifically, NP refers to pain attributable to those pathophysiological processes associated with activation of the peripheral receptive terminals of primary afferent neurones (Ad and C fibres) in response to noxious chemical (inflammatory), mechanical or thermal stimuli (Ekman and Koman, 2004; Julius and McCleskey, 2006). Chemically mediated nociception arising from the activation of nociceptors by pro-inflammatory chemicals released in response to injury or pathology (McMahon et al., 2006) or by a lowering of tissue pH in response to tissue ischaemia from static mechanical (postural) tissue loading or compression (Butler, 2000) represent some of the peripheral mechanisms that might underlie many clinical presentations of musculoskeletal pain including low back pain (LBP). In the absence of a gold standard method with which to diag- nose or classify patients’ pain as being predominantly ‘nociceptive’ such clinical impressions must inevitably be determined clinically. Advocates of mechanisms-based classifications of pain have * Corresponding author. Tel.: þ353 1 221 4467; fax: þ353 1 221 4001. E-mail addresses: k.smart@svuh.ie, k.smart@ucd.ie (K.M. Smart). Contents lists available at SciVerse ScienceDirect Manual Therapy journal homepage: www.elsevier.com/math 1356-689X/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved. doi:10.1016/j.math.2012.03.002 Manual Therapy 17 (2012) 352e357