Background Volleyball and basketball are among the sports with a higher incidence of knee injuries. The inability to maintain a proper alignment of the lower limbs during functional activities could create a knee valgus which predisposes to injury. Thus, the quantification of knee valgus is necessary to guide prevention and clinical interventions.

Objective To establish normative values for dynamic knee valgus during the single leg squat (SLS) in volleyball and basketball athletes.

Design Observational cross-sectional.

Setting Minas Tênis Club, Brazil, youth sports.

Participants 151 athletes (108 male and 43 female) were assessed during national championship preseason. All participants were healthy, with no current pain of lower limb injury and no history of previous lower extremity surgery. The mean age, weight and height were 14.21+2.09; 62.75+14.20 and 173.89+13.42, respectively.

Assessment of risk factors Gender, age and sport.

Main outcome measurements Knee valgus was measured as frontal plane projection angle of the knee (FPPAK) during SLS up to 60° of knee flexion. The mean of three repetitions of SLS from each limb was used for analysis, using SIMI Motion Twinner software. The FPPAK was defined as the connections between ASIS, midpoint of femoral epicondyles and anterior midpoint of the malleolis.

Results The mean FPPAK during SLS for right leg was 7.08+4.0 and 8.68+4.2 for left leg. There were no differences between ages and genders. There were significant differences between sides in both modalities (p<0.000).The basketball athletes had lower FPPAK on the left leg when compared with athletes from volleyball (p<0.000).

Conclusion All athletes showed an inability to maintain proper alignment during dynamic squat. The differences found between modalities may be linked to the specific technique of each sport and are important to guide an intervention focused on injury prevention.