Table 3.

Annual/seasonal incidence of ACL injury in prospective cohort or controlled intervention studies in adolescent female football used for the sample size calculation.

Study	Population	Study design	Number of players in the control group	Number of players with ACL injury (%)
Hewett et al., 1999 [15]	High school	Controlled trial	193	2 (1.04%)
Heidt et al., 2000 [14]	Age 14–18 years	Randomized controlled trial	258	8 (3.10%)
Powell & Barber-Foss, 2000 [24]	High school	Prospective cohort study	6 642	33 (0.50%)
Mandelbaum et al., 2005 [16]	Age 14–18 years	Controlled trial	3 818	67 (1.76%)
Pfeiffer et al. 2006 [17]	High school	Controlled trial	189	0
Steffen et al., 2008 [19]	Age 13–17 years	Randomized controlled trial	947	5 (0.53%)

ACL: Anterior Cruciate Ligament