Intrinsic Risk Factors for Noncontact Anterior Cruciate Ligament Injury in Young Female Soccer Players: A Prospective Cohort Study.

BACKGROUND Previous studies have attempted to determine prognostic factors for predicting the occurrence of noncontact anterior cruciate ligament (ACL) injuries. However, studies on risk factors for noncontact ACL injuries in Asian female soccer players are limited. PURPOSE To identify intrinsic risk factors for noncontact ACL injuries among young female Asian soccer players. STUDY DESIGN Cohort study; Level of evidence, 2. METHODS This study evaluated 145 female Japanese soccer players for potential risk factors for noncontact ACL injury during the preseason medical assessment. In total, 25 variables were examined-including anthropometric data, joint range of motion, muscle flexibility, muscle strength, and balance measurements. Participants were monitored throughout a single season for noncontact ACL injuries diagnosed by physicians. RESULTS Noncontact ACL injuries occurred in 13 knees of 13 players (9%). Lower hamstring-to-quadriceps ratio (0.44 ± 0.07 vs 0.50 ± 0.10; P = .04), greater knee extension muscle strength (3.2 ± 0.5 vs 2.7 ± 0.5 N·m/kg; P < .01), and longer playing experience (10.8 ± 3 vs 8.1 ± 4.2 years; P = .02) were significantly associated with new-onset noncontact ACL injuries in young female soccer players. No statistically significant between-group differences were found for any other variables. CONCLUSION New-onset noncontact ACL injury in young female soccer players was significantly associated with lower hamstring-to-quadriceps ratio, greater knee extension muscle strength, and longer soccer experience. These findings will help develop strategies for preventing noncontact ACL injuries among female soccer players.