Functional Anatomy of the Foot


The Foot

- Purpose
Accept Weight
Allow forward progression of Body


- Functions
Shock Absorber
Rigid Lever Arm
Loose Adapter to adjust to ground
Torque Absorber
Base of Support to maintain balance




Skeletal Structure

28 Bones (26 true bones + 2 sesamoids)

Three Functional units
= Forefoot (Metatarsals + Phalanges)
= Midfoot (3 Cuneiforms, Navicular, Cuboid)
= Hind foot (Talus + Calcaneus)

Weight bearing is evenly distributed between Calcaneus and Metatarsal unit Hallux 2x weight
acceptance of other heads.

Arches (3)
Medial longitudinal
Lateral longitudinal
Transverse Tarsal

Arches are stable to a certain degree by the wedge shaped structure of the bones. The primary (most important) support for the arches is the Ligaments, which control alignment of the bones. During static stance, the alignments have to be assisted by brief periods of muscle activity or else they will stretch. Attachments of muscles support and stabilize the arch during dynamic activities (walking), no ligamentous tension is involved.


Medial Longitudinal Arch (MLA)

Calcaneus / Talus / Navicular / 3 Cuneiforms / 1-3 Rays (metatarsals + digits)
Strong Planter Ligaments hold together the inferior edges. (Spring Ligament holds Navicular to the Sustentacular Tali. Ends of the arches hold together by the planter aponeurosis and the muscles within the foot.
Planter aponeurosis (PA) with the metatarsal joints stabilize the foot during propulsion (heel off – toe off) using the Windlass Mechanism. Planter aponeurosis runs from the Calcaneus along the planter surface of the foot, winds underneath the metatarsal heads and inserts on the bases of each phalanx. PA shortens when the toes are in extension at push off.
This stabilizes the Longitudinal arches. Further stabilization of the lesser tarsus on the tarsal bones through muscle attachment of Tibialis Posterior which stabilizes the MLA through attachments on the Navicular, Cuboid, 3 Cuneiforms, metatarsals 2-4)


Lateral Longitudinal Arch

Calcaneus / Cuboid / 4+5 Metatarsals
Inferior edges held together by the long and short planter ligaments.
Peroneus Longus inserts lateral aspect of 1st cuneiform and MT , which stabilizes lesser tarsus
against tarsus, creating a stable midfoot.


Transverse Tarsal Arch

Cuboid / 3 Cuneiforms / Heads of Metatarsals / Bases of Metatarsals
Series of interlocking bones. Base of 2nd metatarsal locks into an indentation formed by a short second cuneiform. Forms keystone for the Transverse Arch.
Transverse Pedis muscle (transverse head of Adductor Hallicus muscle) stabilizes the forefoot transversely during propulsion. Whit an abnormally foot during propulsion the effectiveness of this muscle.



Articular Structures

Of the 30 articulations in the foot, Five are important.

Talocrural (ankle)
Subtalar
Transverse Tarsal
First Ray
First Metatarsophalangeal Joint.