Professional issue What is ‘manipulation’? A reappraisal David W. Evans a, * , Nicholas Lucas b a Research Centre, British School of Osteopathy, London SE1 1JE, UK b Sydney School of Public Health, University of Sydney, Australia article info Article history: Received 27 November 2008 Received in revised form 3 November 2009 Accepted 21 December 2009 Keywords: Joint manipulation Spinal manipulation Taxonomy Definition abstract Due primarily to its colloquial function, ‘manipulation’ is a poor term for distinguishing one healthcare intervention from another. With reports continuing to associate serious adverse events with manipulation, particularly relating to its use in the cervical spine, it is essential that the term be used appropriately and in accordance with a valid definition. The purpose of this paper is to identify empirically-derived features that we propose to be necessary and collectively sufficient for the formation of a valid definition for manipulation. A final definition is not offered. However, arguments for and against the inclusion of features are presented. Importantly, these features are explicitly divided into two categories: the ‘action’ (that which the practitioner does to the recipient) and the ‘mechanical response’ (that which occurs within the recipient). The proposed features are: 1) A force is applied to the recipient; 2) The line of action of this force is perpendicular to the articular surface of the affected joint; 3) The applied force creates motion at a joint; 4) This joint motion includes articular surface separation; 5) Cavitation occurs within the affected joint. Crown Copyright Ó 2009 Published by Elsevier Ltd. All rights reserved. 1. Introduction Scientific enquiry often requires researchers to consider the foundations upon which important clinical and academic assumptions have been built. For the professions that use manual therapy, few foundations lie as deep as definitions of the very interventions that distinguish manual therapy from other areas of healthcare. It is difficult for practitioners to make rational decisions about the use of an intervention when that intervention is poorly defined or not mechanistically understood. Indeed, the ramifica- tions of this uncertainty may be more far reaching than judgements made by individual clinicians. For example, definitions of healthcare interventions may be used by purchasers to make inferences about the potential efficacy, safety and appropriateness of that intervention, when applied to populations (e.g. Shekelle et al., 1991; Coulter et al., 1996; Gatter- man et al., 2001). Given that clinical trials have so far provided few clear answers to inform the choice of one physical treatment over another, particularly in relation to musculoskeletal problems (Kel- ler et al., 2007; van der Velde et al., 2008), the perceived charac- teristics of an intervention are likely to be used to provide clinical guidance. In addition, with reports continuing to associate serious adverse events with manipulation (e.g. Ernst, 2007), particularly relating to its use in the cervical spine, the term should be used appropriately and in accordance with a valid definition. Manipulation is one intervention for which a satisfactory defi- nition is lacking. Due primarily to its colloquial function, ‘manipu- lation’ is a poor term for distinguishing one physical treatment from another. Indeed, so vague is the term that when used in scientific journals, supplementary details are often required to differentiate ‘real’ manipulation from its manual therapy counterparts (e.g. Keller et al., 2002; Harvey et al., 2003; Skyba et al., 2003; Colloca et al., 2004, 2006; Song et al., 2006). Oversights of this kind may be avoided if what is currently termed ‘manipulation’ were accurately defined. The purpose of this paper is to present features proposed to be necessary components of a valid definition of manipulation. A final definition of manipulation is not offered, but arguments for and against the inclusion of these empirically-derived features are presented as a first step in this direction. 2. Defining manipulation Prior to contemplating a definition of manipulation, it is necessary to consider how a definition should be formed. Estab- lished criteria for a definition are presented in Table 1 and are compared to those criteria that meet the requirements for a description. A useful definition of manipulation should encom- pass all characteristics that empirical research has shown to be universally valid in all parts of the body, yet exclude any * Corresponding author. Tel.: þ44 7853914487. E-mail address: dwe@spinalmanipulation.org.uk (D.W. Evans). Contents lists available at ScienceDirect Manual Therapy journal homepage: www.elsevier.com/math 1356-689X/$ – see front matter Crown Copyright Ó 2009 Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.math.2009.12.009 Manual Therapy 15 (2010) 286–291