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)
  • Formed by the head of the fibula and the posterolateral aspect of the tibia
  • Plane joint with anterior and posterior proximal tibiofibular ligaments
  • Interosseous membrane connects the tibia and fibula
• Distal tibiofibular joint (DTFJ)
  • Formed by the concave face of the tibia and the convex face of the fibula
  • Syndesmosis with anterior and posterior distal tibiofibular ligaments
  • Fibrous fat tissue connects 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
• Trochlea of the talus is wider anteriorly than posteriorly
• In the DTFJ:
  • Dorsiflexion: separation
  • Plantar flexion: approximation

Talocrural Joint

• Mortise formed by the medial and lateral malleoli
• Hinge joint with 1 degree of freedom
• Rest position: 10° plantar flexion
• Close pack: maximal dorsiflexion
• Concave/convex rule:
  • Open kinematic chain: convex rule
  • Close kinematic chain: concave rule

Osteokinematics and Arthrokinematics of the Talocrural Joint

• During dorsiflexion in the open kinematic chain, the dome of the talus is convex, and the distal tibia/fibula is concave
• Concave rule applies during dorsiflexion in the closed kinematic chain
• 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
  • Tibionavicular, tibiotalar, and tibiocalcaneal ligaments
• Lateral stability:
  • Anterior talofibular ligament
  • Posterior talofibular ligament
  • Calcaneofibular ligament
• Dynamic stabilizers: musculature

Kinetics of the Ankle and Foot

• 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 and cuneonavicular joints

Subtalar/Talocalcaneal Joint

• Synovial, gliding joint
• Three separate plane articulations between the talus and calcaneus
• Allows supination and pronation of the ankle
• Pronation: loose pack position, allows foot to absorb shock during loading phase of gait
• Supination: closed pack, creates rigid lever

Subtalar Joint Stability

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

Osteokinematics and Arthrokinematics of the Subtalar Joint

• Osteokinematics: oblique axis, hence pronation and supination
• Pronation: dorsiflexion, eversion, and abduction
• Supination: plantar flexion, inversion, and adduction
• Arthrokinematics:
  • 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, contributes to pronation, supination, and simplified arthrokinematics

Arch Support

• Internal arch:
  • Formed by calcaneus, talus, navicular, medial cuneiform, and 1st metatarsal
  • Support ligaments: plantar calcaneonavicular ligament, 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

Metatarsophalangeal and Interphalangeal Joints

• Function in the closed kinematic chain
• Windlass plantar mechanism:
  • The plantar aponeurosis acts similarly to a windlass mechanism
  • Hyperextended MTPs tighten the plantar aponeurosis
  • Joints the metatarsal and tarsal bones, making them a rigid structure and eventually raising the longitudinal arches