The variation of the Q angle with different positions of the foot.

The Q angle (i.e., the angle between the rectus femoris and the patellar ligament) was measured on 34 healthy volunteers by use of three different methods: (1) a photographic method, (2) a direct method with a goniometer on erect persons, and (3) a direct method on subjects in the supine positions. The Q angle was measured with the foot in different positions with regard to inward and outward rotation and pronation and supination. It was found that the Q angle increased as the foot shifted from outward to inward rotation. The Q angle decreased as the foot shifted from pronation to supination. The reproducibility of the photographic method was good and gave basically the same values as the direct method on erect persons. However, these methods gave values different from those of the direct method on the supine person. Consequently, it is necessary to standardize the position of the foot when measuring the Q angle.