Evaluating influences on classifications of severity for injuries in professional football

Background According to consensus definitions for football surveillance, injury severity is classified from ‘slight’ to ‘career ending’, based on number of days absence from participation. Objective To examine whether different definitions of return to participation (RTP), and playing in matches while injured, affect groupings of injury severity in professional football. Design Secondary analysis of prospective injury data. Setting English league football. Participants Male professional footballers contracted to a Championship, League 1 and League 2 football team (n=78). Interventions 1) RTP, defined as ‘return to full participation in training (RTT)’ and ‘return to match play (RTM)’ in 161 injuries. 2) Presence of pain or symptoms that directly preceded or followed time loss, in 45 episodes of playing while injured. Main outcome measurements Injury severity, measured by the number of days from date of injury to RTP, expressed according to consensus statement severity groupings. Results Median days absence from participation was significantly higher for RTM than RTT, although this did not affect average severity groupings (z=-8.824, P<.001; RTM: mean 15.7±2.3 days [moderate injury], median 6 days [mild injury]; RTT: mean 10.9±2.2 days [moderate injury], median 4 days [mild injury]). Differences were observed in the distribution of injuries grouped according to their severity with the two definitions of RTP. Two thirds of cases where athletes played in matches while injured were reclassified into higher severity groupings when the time spent playing in matches while injured, either directly preceding or following a period of absence, was counted. Conclusions When measured in days, football injury severity is directly influenced by definitions of RTP, and may be affected by match scheduling. Pain or injury symptoms do not contribute towards current severity classifications, yet often precede or follow a period of absence. Therefore, expressions of injury severity in football should encompass more than just absence from participation.