Normal Foot Anatomy

A normal foot has a defined, flexible curve that allows for even weight distribution and efficient shock absorption. 

• Arch Structure: The medial longitudinal arch is the most prominent, formed by the calcaneus, talus, navicular, three cuneiforms, and the first three metatarsals.
• Support System: Supported by the plantar fascia, spring ligament, and tendons, particularly the posterior tibial tendon.
• Function: It is dynamic, flattening slightly to absorb impact and becoming rigid for propulsion. 

Flat Foot (Pes Planus)

Flatfoot occurs when the medial longitudinal arch collapses, causing the entire sole to touch the ground. 

• Anatomical Changes: The heel often tilts outward (valgus), the ankle rolls inward (overpronation), and the navicular bone may stick out.
• Types:
  • Flexible Flat Foot: The arch is present when sitting or on tiptoes but disappears upon standing.
  • Rigid Flat Foot: The arch is absent in all positions, often due to bony abnormalities.
• Causes: Genetic factors, weak tendons (posterior tibial tendon dysfunction), aging, or obesity.