The aim of the present study was to investigate three important mal-alignments (pronation, tibial torsion and Q angle) as risk factors in ACL tear in professional female athletes. Twenty ACL – injured females (age 24.90 ? 5.75 years, height 167.05 ? 6.58 cm, mass 60.88 ? 5.58 and athletic experiences 7.70 ? 4.41 years) and 20 uninjured females (age 24.80 ? 5.59 years, height 166.15 ? 6.39 cm, mass 60.20 ? 6.08 and athletic experience 7.00 ? 3.69 years who were the injured females' counterparts based on their age, sport field and injured limb) participated in this study. Navicular drop, tibial torsion and Q angle were measured in both limbs. Mechanism of injury was non-contact in about 90% of cases. In 17 cases (58%), a medial meniscus injury was reported. The findings showed a significant difference in pronation and tibial torsion between groups (P<0.05). These was no significant difference in Q angle between groups (P<0.05). Also there was no significant difference in lower extremity alignment between injured and uninjured limbs of ACL-injured group. Therefore, it is suggested that the biomechanical risk factors are identified and athletes with hyper-pronation and internal tibial torsion are screened as they may be predisposed to ACL injury. It is also necessary for coaches to apply corrective and prevention programs.