2-Dimensional Foot Shape
A medial axis (skeleton) of a foot outline is used to summarize the 2-dimensional foot shape. The medial axis corresponds to the approximate midline of the long direction. The medial axis flexes in most feet, that is, most feet are outflared. Three regression lines were fitted to the medial axis, and the degree of outflare is quantitized by using the posterior flexion angle.
The distribution of the posterior flexion angle is a normal distribution with a mean of 8.4 degrees in males (8.2 in females) and with SD of 4.03 (3.79) degrees. In the medial axis of shoe last outline, the posterior flexion angle is 0 degrees.