PURPOSE: To prospectively evaluate risk factors for acute time-loss @entity3331 , in particular @entity130 , in female youth football players. METHODS: Risk factors were studied in 4556 players aged 12-17  years from a randomised controlled trial during the 2009 season. Covariates were both intrinsic (body mass index, age, relative age effect, onset of menarche, previous @entity131 or @entity130 , current knee complaints, and @entity130 ) and extrinsic (no. of training sessions/week, no. of matches/week, match exposure ratio, match play with other teams, and artificial turf exposure). Hazard ratios (HRs) and 95  % confidence intervals (CIs) were calculated from individual variable and multiple Cox regression analyses. RESULTS: Ninety-six acute @entity3331 were recorded, 21 of them @entity130 . Multiple Cox regression showed a fourfold higher @entity130 rate for players with @entity130 (HR 3.57; 95  % CI 1.48-8.62). Significant predictor variables for @entity131 were age >14  years (HR 1.97; 95  % CI 1.30-2.97), knee complaints at the start of the season (HR 1.98; 95  % CI 1.30-3.02), and @entity130 (HR 1.96; 95  % CI 1.22-3.16). No differences in injury rates were seen when playing on artificial turf compared with natural grass. CONCLUSION: Female youth football players with a @entity130 had an increased risk of @entity130 and @entity131 . Older players and those with knee complaints at pre-season were more at risk of @entity131 . Although the predictive values were low, these factors could be used in athlete screening to target preventive interventions. LEVEL OF EVIDENCE: II.

Risk factors for XXXX in female youth football.

@entity131 :: ('MESH:D001930', 'Disease') :: ['acute knee injury'] @entity3331 :: ('MESH:D007718', 'Disease') :: ['knee injuries', 'knee injury'] @entity130 :: ('MESH:D014947', 'Disease') :: ['familial disposition of ACL injury', 'ACL injury', 'ACL injuries']
@entity131 :: (MESH:D001930,Disease) :: ['acute knee injury']
