What determines the magnitude of the Q angle? A preliminary study of selected skeletal and muscular measures

Context: Q-angle size has been found to correlate poorly with skeletal measures of pelvic breadth and femur length. Because the patella is exposed to the forces of quadriceps contraction, muscular forces might also affect Q-angle magnitude. Objective: To compare bilateral measurements of the Q angle with selected skeletal and muscular strength measures. Design: In vivo study of anthropometric and quadriceps peak torque measures. Setting: Research laboratory. Participants: Thirty-four healthy men and women, mean age 20.9 +/- 2.7 years. Main Outcome Measures: Q angles, pelvic breadths, femur lengths, and peak torque during dynamic knee-extension exercise, normalized to body weight. Results: Significant differences in Q-angle magnitude, femur length, and peak torque(BW) were observed between sexes, but not between limbs. Pelvic breadth did not differ significantly between sexes. Correlational analysis revealed a weak, yet significant, linear relationship between Q angle and peak torque(BW) in the right lower limb. Conclusions: These findings lend some support to the notion that Q-angle magnitude is inversely related to quadriceps strength.