Quadriceps femoris muscle angle: normal values and relationships with gender and selected skeletal measures.

The quadriceps femoris angle ("Q angle") has been implicated as a source of several knee disorders, but values for normal knees have not been adequately documented in the literature. This study was designed to provide clinicians with normal values and information regarding the relationships between Q angle, gender, and selected anatomical measurements. The Q angles of 100 individuals (50 men, 50 women), who had no history of knee disorders, were measured goniometrically. The hip widths and femur lengths of all subjects were measured with calipers. The mean Q angle for women was 15.8 +/- 4.5 degrees and for men was 11.2 +/- 3.0 degrees. Using a point biserial correlation, we found a relationship between gender and Q angle (r = -.517) that remained significant (p less than .01) when the effects of femur length and hip width were controlled. The relationships identified between Q angle and the anatomical measurements were no longer significant when the effect of gender was eliminated. The results substantiate the belief that women have larger Q angles than men, but they fail to provide clinicians with an anatomical explanation or new predictor of Q angle.