Bilateral within-subject Q angle asymmetry in young adult females and males.

Previous investigations of the quadriceps angle (or Q angle) and its relationship to knee disorders have yielded equivocal results. Methodological differences may account for some of the observed discrepancies, but so too may the tendency for investigators to rely on between-group rather than within-subject research designs. The purpose of this investigation was to study the between-group (male versus female) and within-subject (right versus left lower limb) differences in Q angle measures in subjects with no history of knee disorders. The right and left Q angles of fifty young men and women were measured goniometrically with subjects standing in an erect, weight-bearing position. In males, there was little disparity in the magnitude of the Q angle between the right (9.5 degrees +/- 4.6) and left (10.4 degrees +/- 5.7) lower limb. Similarly, in females, the mean value for the right Q angle (10.5 degrees +/- 4.2) was only slightly smaller in magnitude than that of the left (12.2 degrees +/- 5.2). A 2 x 2 ANOVA revealed no significant gender (p < 0.17) or right to left lower limb (p < 0.19) differences. However, when the data for each subject was examined on an individual basis, the magnitude of the right and left Q angles differed by 4 degrees or more in 24 subjects. In 10 subjects, this difference ranged from 8.0 degrees to 10.3 degrees. For the majority of subjects the left Q angle was greater in magnitude than the right Q angle. These results suggest that (I) the assumption of symmetry in right versus left lower limb Q angle measures may be erroneous, (II) statistical comparisons of mean values may not be the best method by which to analyze Q angle data, and (III) further investigation of bilateral within-subject Q angle asymmetry is warranted.