Anatomy of the Ankle and Foot

Ankle and Foot Function

• Provide a stable base while conforming to uneven surfaces
• Flexible to absorb stress and adapt to the ground
• Rigid to withstand propulsive forces and push off
• Weight bearing during walking, running, and standing
• Allows positioning of the foot

Tibiofibular Joints

• Proximal tibiofibular joint (PTFJ):
  • Plane joint
  • Anterior and posterior proximal tibiofibular ligaments
  • Interosseous membrane
• Distal tibiofibular joint (DTFJ):
  • Syndesmosis
  • Anterior and posterior distal tibiofibular ligaments
  • Fibrous fat tissue connecting the tibia and fibula

Arthrokinematics of the Tibiofibular Joints

• Slight gliding motion in the PTFJ during osteokinematics of the ankle and knees:
  • Dorsiflexion: cranial glide
  • Plantar flexion: caudal glide
  • Knee flexion: forward glide
  • Knee extension: posterior glide
• DTFJ:
  • Dorsiflexion: separation
  • Plantar flexion: approximation

Talocrural Joint

• Mortise by medial malleolus and lateral malleolus
• Hinge joint, 1 degree of freedom
• Rest position: 10 degrees plantar flexion
• Close pack: maximal dorsiflexion
• Concave/convex rule:
  • Open kinematic chain: convex rule
  • Close kinematic chain: concave rule

Arthrokinematics of the Talocrural Joint

• During dorsiflexion in OKC, the dome of the talus is convex, and the distal tibia/fibula is concave
• Talus (convex): anterior roll, posterior glide
• Mortise (concave): anterior roll, anterior glide

Talocrural Joint Stability

• Static stabilizers (passive structures):
  • Mortise and talar shape
  • Gravity
  • Capsule and ligaments
  • Medial stability: deltoid ligament
  • Lateral stability:
    • Anterior talofibular ligament
    • Posterior talofibular ligament
    • Calcaneofibular ligament
• Dynamic stabilizers: musculature

Kinetics

• Dorsiflexion:
  • Tibialis anterior
  • Extensor digitorum longus
  • Extensor hallucis longus
• Plantar flexion:
  • Gastrocnemius
  • Soleus
  • Tibialis posterior
  • Peroneus longus and brevis
  • Plantaris
  • Flexor hallucis longus

Foot Anatomy

• Rearfoot: calcaneus, talus
• Midfoot: navicular, cuboid, 3 cuneiforms
• Forefoot: metatarsals and phalanges

Foot Joints

• Subtalar/talocalcaneal joint
• Mediotarsal (Chopart's) joint:
  • Talonavicular
  • Calcaneocuboid
  • 5 tarsometatarsal joints
  • Cubonavicular, cuneonavicular

Subtalar Joint

• Talus on calcaneus
• Synovial, gliding joint
• Three separate plane articulations between the talus superiorly and the calcaneus inferiorly:
  • Posterior
  • Medial
  • Anterior

Subtalar Joint Stability

• Interosseous talocalcaneal ligament
• Lateral talocalcaneal ligament
• Posterior talocalcaneal ligament
• Medial talocalcaneal ligament

Ankle Osteokinematics

• Osteokinematics of the subtalar joint:
  • Oblique axis, hence pronation and supination
  • Pronation: dorsiflexion, eversion, and abduction (lowering of the arch)
  • Supination: plantar flexion, inversion, and adduction (elevation)

Arthrokinematics of the Subtalar Joint

• Posterior facet of calcaneus: convex rule (OKC)
• Anterior facet of calcaneus: concave rule (OKC)

Midtarsal/Chopart's Joint

• Talonavicular and calcaneocuboid joints
• Osteokinematics: combined with subtalar joint, also contributes to:
  • Pronation
  • Supination
  • Simplified arthrokinematics

Arch Structures

• Internal arch:
  • Formed by calcaneus, talus, navicular, medial cuneiform, and 1st metatarsal
  • Support ligaments:
    • Plantar calcaneonavicular ligaments
    • Interosseous talocalcaneal ligament
  • Support muscles:
    • Tibialis posterior
    • Peroneus longus
    • Flexor hallucis longus
    • Abductor hallucis
• External arch:
  • Formed by calcaneus, cuboid, and 5th metatarsal
  • Support ligament:
    • Plantar calcaneocuboid ligament
  • Support muscles:
    • Peroneus longus
    • Peroneus brevis
    • Abductor digiti minimi
• Anterior arch:
  • Formed by metatarsal heads
  • Support ligaments:
    • Intermetatarsal ligament
  • Support muscles:
    • Adductor hallucis