L12

Arches of the Foot

• The foot has three arches: medial longitudinal, lateral longitudinal, and transverse.
• The medial longitudinal arch is higher, more mobile, and resilient. It's formed by the calcaneus, talus, navicular, three cuneiforms, and three medial metatarsals.
• The lateral longitudinal arch bears more weight and rests on the ground when standing. It's made up of the calcaneus, cuboid, and the lateral two metatarsals.
• The transverse arch runs across the foot from side to side. It's formed by the cuboid, cuneiforms, and bases of the metatarsals. The medial and lateral longitudinal arches act as pillars supporting the transverse arch.

Arch Support

• Keystone: The middle stone, wedge-shaped, supporting the arch.
• Staples: Metal staples bind the lower edges of stones to prevent separation.
• Tie beams: Connect the ends of the arch to prevent separation.
• Suspension bridges: Multiple supports suspend the arch from above.

Factors Maintaining the Arches

• Shape of bones
• Staples
• Tie beams
• Slings

Medial Longitudinal Arch - Supports

• Summit: Talus (keystone) transfers body weight to other bones.
• Posterior pillar: Short and sturdy calcaneus.
• Anterior pillar: Heads of medial three metatarsals.

Staples

• Calcaneo-navicular ligament (spring ligament)
• Tibialis posterior tendon

Tie Beams

• Plantar aponeurosis
• Flexor digitorum brevis
• Abductor hallucis
• Flexor hallucis longus
• Flexor digitorum longus

Suspension

• Tibialis anterior
• Tibialis posterior
• FDL
• FHL
• Medial ligament (deltoid ligament) of ankle joint

Lateral Longitudinal Arch - Supports

• Summit: Cuboid (keystone)
• Posterior pillar: Calcaneus
• Anterior pillar: Two metatarsals

Staples

• Lateral part of plantor ligaments (calcaneo-cuboid)

Tie Beams

• Plantar aponeurosis
• Flexor digitorum brevis
• Abductor digiti minimi
• Flexor digitorum longus
• Flexor digiti minimi brevis (lateral part)

Suspension

• Peroneus longus
• Peroneus brevis

Transverse Arch

• Shape: Wedge-shaped intermediate cuneiform.
• Staples: Deep transverse ligaments, long plantar ligament, short plantar ligament.

Tie Beam

• Tendon of Fibularis longus
• Suspension bridge: Fibularis tertius, brevis & tibialis anterior

Function of Arches of Foot

• Weight distribution
• Shock absorption
• Protection of soft tissues against pressure
• Acts as a spring during walking and running

Deformities of Foot

• Pes cavus (high arched foot): Exaggerated medial and lateral arches; often caused by muscle imbalance, sometimes from poliomyelitis.
• Pes planus (flat foot): Depressed medial longitudinal arch, leading to forefoot displacement laterally.