Sports concussion can be defined as a complex clinical syndrome precipitated by traumatic forces to the brain sus- tained during participation in sport. 2 The current consensus opinion is that it reflects a nonstructural injury, character- ized by a graded set of clinical and cognitive features that are typically short-lived and resolve spontaneously. 20 While the implication is that concussed athletes would be expected to recover uneventfully, a number of potential short- and long-term complications have been described. These include impaired performance and increased risk of injury, acute progressive diffuse cerebral edema, 5 prolonged symptoms 26 or symptoms of depression, 12 and cumulative cognitive dete- rioration. 11,16 Moreover, it has widely been suggested that the risk of adverse outcomes after sports concussion is greatest when a concussed athlete is returned to play prematurely. 4 Consequently, it is important for treating physicians to ensure that concussed athletes are fully recovered before allowing them to return to play. The main problem in the clin- ical setting, however, is that there is no single, objective, quan- titative criterion to measure recovery after concussive injury. The criteria by which return to play decisions are made after concussion have long been a contentious area of sports medicine. Although numerous guidelines have been proposed, these are based on limited scientific data. 14 One of the fundamental paradigm shifts of the current Concussion in Sport Group recommendations was to move the concept of return to play from anecdotal injury grading scales and arbitrary exclusion periods to one of individual- ized assessment using a combination of clinical symptoms and brief cognitive testing. 2,20 A Prospective Study of Postconcussive Outcomes After Return to Play in Australian Football Michael Makdissi,* † MBBS, PhD, Paul McCrory, † MBBS, PhD, Antony Ugoni, † BSc(Hons), MSc, David Darby, ‡ MBBS, PhD, and Peter Brukner, † MBBS From the † Centre for Health, Exercise and Sports Medicine, University of Melbourne, Parkville, Victoria, Australia, and ‡ CogState Ltd, Melbourne, Victoria, Australia Background: Decisions regarding safe return to play after concussion in sport remain difficult. Objective: To determine whether a concussed player returned to play using an individual clinical management strategy is at risk of impaired performance or increased risk of injury or concussion. Study Design: Cohort study; Level of evidence, 3. Methods: All elite Australian football players were followed for 4 seasons. Players were recruited into the study after sustaining a concussive injury. Outcome measures included performance statistics (disposals per hour match-time), injury rates, and recur- rence of concussion on return to play. A subset of players had brief screening cognitive tests performed at baseline and after their concussion. Noninjured players matched for team, position, age, and size were chosen as controls. Results: A total of 199 concussive injuries were observed in 158 players. Sixty-one concussive injuries were excluded from analysis because of incomplete data (45 players) or presence of concurrent injury (16 players). Of the 138 concussive injuries assessed, 127 players returned to play without missing a game (92%). The remainder of concussed players returned to play after missing a single game (8%). Overall, there was no significant decline in disposal rates in concussed players on return to com- petition. Furthermore, there were no significant differences in injury rates between concussed and team, position, and game- matched controls. In the subset of players who had completed screening cognitive tests, all had returned to their individual baseline performance before being returned to play. Conclusion: Return to play decisions based on individual clinical assessment of recovery allows safe and appropriate return to sport following a concussive injury. Keywords: brain trauma; concussion; Australian football 877 *Address correspondence to Michael Makdissi, MBBS, PhD, Univeristy of Melbourne, Centre for Health, Exercise, and Sports Medicine, Parkville, Victoria, Australia 3010 (e-mail: makdissi@unimelb.edu.au). No potential conflict of interest declared. The American Journal of Sports Medicine, Vol. 37, No. 5 DOI: 10.1177/0363546508328118 © 2009 American Orthopaedic Society for Sports Medicine