Objectives:In a competitive sport situation, not only the exertions of performance but also the incidence of injury can be influenced by psychological factors. In recent years, the focus on anterior cruciate ligament (ACL) injury prevention has increased and many studies exploring risk factors for ACL injury have been published. However, the influence of psychological factors on ACL injuries is poorly documented. The purpose of this study was to investigate the relationship between psychological competitive ability and incidence of ACL injury among high school female athletes.Methods:A 3-year prospective cohort study was conducted with 220 high school female handball or basketball players. All subjects were 15 years old and included 77 handball players and 143 basketball players. At baseline, psychological competitive ability was assessed by a self-administered questionnaire, the Diagnostic Inventory of Psychological Competitive Ability (DIPCA.3). This inventory measures an athlete’s psychological abilities to fully display their skills and talents during competition via 52 questions categorized into 12 scales: Patience, Aggressiveness, Volition for self-realization, Volition for winning, Self-control, Ability to relax, Concentration, Confidence, Decision, Predictive ability, Judgment, and Cooperation. After the baseline examination was performed at high school entry, all players were followed for 36 months to register any subsequent incidence of ACL injury. We compared the differences in psychological competitive ability between injured and uninjured players using an unpaired t-test. Values of p < 0.05 were considered statistically significant. The purpose of this study was explained to the subjects and their parents and written informed consent to participate was obtained from them. This study was approved by the ethics committee of our institution.Results:In the present study, 20 of the 220 players (9.1%) suffered an ACL injury during the 3-year observation period. Eighteen of the 20 injured players sustained a non-contact injury to her knee. Eleven players were injured during the game and 9 players were injured during the practice. Between injured and uninjured players, injured players had significantly higher total DIPCA.3 scores [172.7 ± 18.3 points in injured players and 157.9 ± 20.9 points in uninjured players (p<0.001)]. Regarding the specific scales, injured players scored significantly higher on Patience, Aggressiveness, Volition for self-realization, Predictive ability, Judgment, and Cooperation. However, no significant differences were observed on Volition for winning, Self-control, Ability to relax, Concentration, Confidence and Decision.Conclusion:It is reported that players displaying higher competitive levels of performance or players with higher self-esteem in their own performance score higher on DIPCA.3. In the present study, DIPCA.3 scores were significantly higher in injured players compared with uninjured players. Among the high-scoring players, a strong emphasis on improvement of their performance may force them into situations associated with injury risk. The results of the present study suggest that psychological factors are associated with the incidence of ACL injury.