Figure 3From: A protocol for classifying normal- and flat-arched foot posture for research studies using clinical and radiographic measurements Arch index. Footprint with reference lines for calculating the arch index. The length of the foot (excluding the toes) is divided into equal thirds to give three regions: A – forefoot; B – midfoot; and C – heel. The arch index is then calculated by dividing the midfoot region (B) by the entire footprint area (i.e. Arch index = B/[A+B+C]).Back to article page