Association of quadriceps and hamstrings cocontraction patterns with knee valgus angle in professional female athletes

 knee valgus angle (KVA) maybe a predictor of non-contact anterior cruciate ligament (ACL) injuries. The purpose of this study was to investigate the relationship between quadriceps and hamstrings cocontraction patterns with knee valgus angle in professional female athletes.  

 Fifty-six female athletes (mean ± SD age, 20.5 ± 1.99 years; height, 169.28 ± 7.25 cm; body mass, 60.05 ± 10.06 kg) participated. Surface electromyographic data from the medial and lateral hamstrings and quadriceps and lower extremity kinematics were recorded during the drop jump task. Lateral and medial quadriceps-to-hamstrings (Q:H) cocontraction indices, the ratio of medial-to- lateral Q:H cocontraction, normalized root mean square electromyographic data for medial and lateral quadriceps and hamstrings, and knee valgus angle at initial contact were calculated and used in data analyses. Pearson correlation analyses were performed to determine the relationships between quadriceps and hamstrings cocontraction patterns and knee valgus angle at initial contact (P≤0.05).

 Medial quadriceps-to-hamstrings (Q: H) cocontraction indices and the ratio of medial-to- lateral Q: H cocontraction were found to be correlated with knee valgus angle (P = 0.001 and P = 0.000, respectively).  No correlation between lateral Q: H cocontraction and knee valgus angle was found (P = 0.799).

 Medial-to-lateral Q: H cocontraction appears to be unbalanced in female athletes, which may limit their ability to resist abduction loads. Because higher abduction loads increase strain on the ACL, restoring medial-to-lateral Q: H cocontraction balance in women may help reduce ACL injury risk.