Matching the choice of injury/illness definition to study setting, purpose and design: one size does not fit all!

What constitutes a ‘recordable event’ is arguably the most critical methodological factor affecting the results of sports injury and illness surveillance studies. Although numerous consensus statements have attempted to standardise surveillance methodology,1–6 there remains considerable variation in current definitions of injury. Underlying the choice of definition are a number of practical and theoretical issues, including the duration and setting of surveillance, the available resources, the type of injuries and illnesses of interest, how data are to be collected and what they are to be used for. It is also highly desirable that results are comparable between studies; both within and between sports. Above all, however, surveillance data must be valid. As no single definition is likely to suit all needs, the purpose of this article is to review the strengths and limitations of the three most commonly used definitions in sports epidemiology and to examine their appropriateness depending on the context and objectives of surveillance. We focus particularly on methods of data collection, as this may have important consequences on the reliability of data. Consensus recommendations have been made for several sports, including cricket,1 football (soccer),2 rugby union,3 tennis,4 thoroughbred horse racing5 and most recently, for athletics.6 Earlier statements have focused solely on injuries, which may be defined as physical complaints resulting from the transfer of energy at a rate or in an amount that exceeds that tissue's threshold for damage.6 ,7 Recently they have also been expanded to include illnesses, defined as physical or psychological complaints that are unrelated to injury.6 However, common to all statements (with the notable exception of cricket) is the recommendation that a recordable incident should be defined as any physical or psychological complaint resulting from relevant sports participation regardless of its consequences, but that …