Functional Anatomy of the Ankle and Foot

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Functional Anatomy of the Ankle and Foot

• Han-Yu Chen, PT, PhD
• Department of Physical Therapy, Hungkuang
  University

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Contents

• Introduction
• Ankle joint
• Subtalar joint
• Midtarsal joint
• First ray

• Second, third and fourth rays
• Fifth ray
• Metatarsophalangeal joint
• Interphalangeal joints

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Introduction

• Foot and ankle contain 28 bones with 55
  articulations.
• Heel-strike dissipate ground reaction force and
  become a mobile adaptor.
• Late stance transfer body weight from rearfoot
  to forefoot and become a rigid level arm.
• Variation in axis positioning result in uni-,
  bi-, or triplanar motion.

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Motion-open chain
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Motion-open chain
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Motion-closed chain
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Motion-closed chain
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Combined movement

• Articulation moves with a combination of spin,
  glide, rock.---multiple axes
• Pronation
• Abduction, dorsiflexion, eversion
• Supination
• Adduction, plantarflexion, inversion

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Ankle joint (Talocrural joint)

• Axis
• 8o to the transverse plane
• 20o-30o to the frontal plane
• Vary the axis throughout the ankles range

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Shift ankle axis during movement

• Irregular curved contour of the medial talus
  allows for a constant repositioning of the axis
  as the ankle moved
• All axes are close to the midpoint of a line
  connecting the tips of the malleoli

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Plantarflexion

• Plantarflexion is limited by the
• Anterior talofibular ligament and
• Osseous block from contact between the posterior
  tubercle of the talus and tibia

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Dorsiflexion

• Dorsiflexion is limited primarily by tension in
  the
• Triceps surae and
• Posterior deltoid ligament and
• Posterior talofibular ligament
• Bony block between talus (wide in anterior part)
  and distal tibia and fibula

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Subtalar joint (1)

• Between talus and calcaneus
• May have 1 (most mobile), 2, or 3 (less mobile)
  articulations
• Axis (allow triplanar motion with equal amount
  Ever/Inver and ADD/ABD)
• 42o to the transverse plane (20-68.5o)
• 23o to the sagittal plane (4-47o)

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Subtalar joint (2)

• Axis lines 45o to transverse plane
• 1o rear foot motion will produce 1o tibia
  rotation
• Axis lines 70o to transverse plane (high axis)
• 2o rear foot eversion will produce 8o tibia
  internal rotation

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Subtalar joint with 2 articulations

• Remain congruent throughout pronation and
  supination
• Motion is limited by the
• Posterior and lateral talocalcaneal ligament
• Interosseous ligament

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Subtalar joint with 1 or 3 articulations

• 1 articulation
• Most mobile
• Without the constraint from interosseous ligament
  
• 3 articulations
• Supination
• Alteriolateral talus collided with alteriolateral
  calcaneus
• Pronation
• Rapid joint incongruity prevent motion

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Midtarsal joint (1)Transverse tarsal joint,
Chopart joint

• Between talonavicular and calcaneocuboid joint
• Oblique midtarsal joint axis
• 52o to the transverse plane
• 57o to the sagittal plane
• Allow more dorsi/plantarflexion, ABD/ADD
• Longitudinal midtarsal joint axis
• 15o to the transverse plane
• 9o to the sagittal plane
• Allow pure Ever/Inver

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Midtarsal joint (2)

• Supination is limited by soft tissue
• Pronation is limited by osseous locking to
  prevent excessive motion and ligaments
• Cuboid contact with calcaneus

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First Ray

• Medial cuneiform bone and 1st metatarsal bone
• Axis
• 45o to frontal and sagittal plane
• Allow equal amount dorsi/plantarflexion and
  Ever/Inver
• Limited ABD/ADD
• Motion is limited by soft tissue tension

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Second, third, and fourth Ray

• 2nd, 3rd ray
• Respective cuneiform bone and metatarsal bone
• 4th ray
• Only metatarsal bone
• Axis
• Unclear, in sagittal plane
• Allow dorsiflexion / plantarflexion
• Ever / Inversion

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Fifth Ray

• Only metatarsal bone
• Axis
• 20o to transverse plane and 35o to sagittal plane
• Allow dorsiflexion / plantarflexion
• Motion is limited by soft tissue tension

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Metatarsophalangeal joints

• Axis
• Allow pure dorsi/plantarflexion (functional
  importance) and ABD/ADD

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Controversy in ABD/ADD movement

• 2nd metatarsal bone as axis (Fig A)
• Mid-sagittal plane of body (Fig B,C)

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Interphalangeal joints
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Muscles
plantarflexion
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Tibialis posterior and Tibialis anterior
Dorsi-flexion
inversion
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Peroneus longus and brevis
eversion
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Flexor digitorum longusFlexor hallucis brevis
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Adductor hallucisFlexor digitorum brevis
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Lumbricles Interossei