Background Knee injuries in soccer are common regardless of age, gender or playing level. The injury that draws most attention is the anterior cruciate ligament tear and adolescent females seem to have the highest risk. Le Gall and associates (2009) reported 12% of incidence in female soccer players. Several potential risk factors, for example anatomical and biomechanical factors, have repeatedly been discussed in the literature, but lack scientific evidence.

Objective assess the potential predictors of frontal plane knee angle (FPKA) and the interplay between them, through a non-linear statistical model (Classification and Regression Tree-CART).

Design Observational cross sectional.

Setting A professional female soccer team was evaluated in Sports Prevention and Rehabilitation Laboratory (LAPREV) at Federal University of Minas Gerais (CENESP-UFMG).

Participants 19 female soccer athletes, mean age 18.27 (2.79) years were included in this study. All participants were healthy, with no current complaints of lower limb injury or pain and no history of previous lower extremity surgery.

Assessment of risk factors The independent variables were shank-forefoot alignment (SFA), hip abductor torque, hip passive internal rotation (HPIR).

Main outcome measurements The FPKA during three single leg squat with dominant leg in front of a camera (reflexive marcs were located in ASIS, femoral condyles and in a middle point of the medial and lateral maleolus).

Results The HPIR was the main predictor of High-FPKA. 15.8% presented high-FPKA with a HPIR <26.55°. Those with HPIR >33.55° and SFA>17.10° also presented High-FPKA (21%). The model's estimate risk was 15% and the sensibility and specificity were 78% and 84% respectively.

Conclusion The extreme low and great ranges available of HIPR associated with high values of SFA were predictor of knee malalignment in frontal plane. Also the SFA must be considered part of athletes' preseason assessment.