Quadriceps angle and risk of injury among high school cross-country runners.

Design: Prospective cohort study.

Objectives: To determine the relationship between quadriceps angle (Q-angle) and risk of lower extremity injury among adolescent cross-country runners.

Background: No consensus exists on the role of the Q-angle as a risk factor for lower-extremity overuse injury, especially the effect of large Q-angle or right-left Q-angle difference.

Methods And Measures: The Q-angles of 393 high school cross-country runners, 13 to 19 years of age, were goniometrically measured in a static, standing position with quadriceps relaxed. The runners were followed during a cross-country season to assess lower extremity injuries resulting from running in practices or competitions.

Results: Runners with a Q-angle >20 degrees were at 1.7 times greater risk of injury (relative risk [RR], 1.7; 95% confidence interval [CI]: 1.2, 2.4) compared with runners whose Q-angle was 10 degrees to <15 degrees . The RR estimates were similar among girls and boys. Runners with >4 degrees absolute right-left Q-angle difference were at 1.8 times greater risk (RR, 1.8; 95% CI: 1.4, 2.5) compared to runners with a smaller difference. Runners with a Q-angle >20 degrees were more likely to injure their knee, while runners with >4 degrees Q-angle difference were more likely to injure their shin. Runners with a Q-angle >20 degrees had greater time lost due to injury.

Conclusions: High school cross-country runners with large or asymmetric Q-angles may be at greater risk for running injury. Our study suggests that Q-angle measurement be included in preseason screening exams.