Background Knee valgus during landing has been identified as a risk factor for anterior cruciate ligament injury. Component motions of knee malalignment are femoral internal rotation and adduction, tibial abduction and ankle eversion. This excessive eversion is frequently attributed to the presence of forefoot varus alignment. Therefore, the proximal and distal segments of the kinetic chain must be assessment to better understanding of high frontal plane knee angle – FPKA (2D valgus analysis).

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

Design observational cross-sectional.

Setting all testing took place at Minas Tênis Club and at Sports Injury Prevention and Rehabilitation Laboratory – LAPREV in youth and elite sports.

Participants 72 volleyball and basketball athletes (22 female and 50 male) were assessed during national championship preseason. All participants were healthy, with no current complaints of lower limb injury or pain and no history of previous lower extremity surgery. The average+SD age, height and mass of the athletes was 16.7+4.6 years, 179.7+14.7 cm, 68.6+16 Kg.

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

Main outcome measurements frontal plane knee angle during landing from countermovement jump.

Results the SFA was the main predictor of High-FPKA. 75% of the athletes with SFA <10.9° and abductor torque <109 Nm/kg and 83% of the athletes with SFA >17° and hip passive IR ROM >47° presented High-FPKA.

Conclusion the SFA and interaction between it with reduced abductor torque and great hip passive IR ROM were predictors of knee malalignment in frontal plane. Thus, measuring foot alignment must be simultaneous with hip joint dysfunctions and should be part of athletes' preseason assessment.