Objective: The purpose of this study was to evaluate the effect of hip rotation on the electrical activity of the Vastus Medialis Obliquus (VMO), Vastus Lateralis Obliquus (VLO) and Vastus Lateralis Longus (VLL) muscles when squatting with 45º knee flexion, in association with the neutral position, 45º lateral rotation and 15 and 30º medial hip rotation. Method: 27 women were evaluated: 15 healthy women as a control group (21.1 ± 2.1 years) and 12 subjects with patellofemoral pain syndrome (PFPS) (21.0 ± 2.3 years). The electrical activity of the quadriceps muscle was detected using simple active differential surface electrodes, an eight-channel electromyography system and the Aqdados 7.2.6 software. The data were normalized by the mean squatting percentage at 75º with the hip in the neutral position RMS (µV). Two-way ANOVA with repeated measurements followed by the Tukey post hoc test (p<0.05) was used for statistical analysis. Results: The results revealed interaction between groups and muscles (p=0.00), independent of hip position (p=0.39), and there was no interaction between groups and hip positions (p=0.96). The VMO and VLL muscles of the PFPS group showed significantly greater electrical activity than did VMO (p=0.00) and VLL (p=0.04) muscles from the control group. On the other hand, the electrical activity of the VLO muscle did not present any significant difference between the groups (p=0.99). Conclusion: Under the experimental conditions utilized, the results suggested that hip rotation did not alter the electrical activity of the quadriceps portions in either group when squatting with 45º knee flexion.
knee; quadriceps muscle; patellofemoral pain syndrome; electromyography; anterior knee pain
