Foot and Ankle Anatomy

Foot & Ankle Bones - Skeletal Blueprint

• Tarsal Bones (7): Hindfoot (Talus, Calcaneus); Midfoot (Navicular, Cuboid, 3 Cuneiforms - Medial, Intermediate, Lateral).
  • 📌 Mnemonic: Tiger Cubs Need MILC. (Talus, Calcaneus, Navicular, Medial, Intermed, Lat cuneiforms, Cuboid).
• Metatarsals (5): Numbered I-V (medial to lateral).
  • 1st: shortest, thickest.
  • 5th: styloid process (peroneus brevis; avulsion #).
• Phalanges (14):
  • Great Toe (Hallux): 2 (proximal, distal).
  • Lesser Toes (II-V): 3 each (proximal, middle, distal).
• Sesamoids: Typically 2, under 1st metatarsal head.

⭐ Talus: no muscle attachments; blood supply via neck (↑AVN risk with #).

Foot & Ankle Joints & Ligaments - Stability Straps

• Ankle (Talocrural) Joint: Hinge; Tibia, Fibula, Talus.
  • Movements: Dorsiflexion/Plantarflexion.
  • Ligaments:
    • Medial (Deltoid): Tibionavicular, Tibiocalcaneal, Ant. & Post. Tibiotalar. Very strong.
    • Lateral: Anterior Talofibular (ATFL) 📌, Calcaneofibular (CFL), Posterior Talofibular (PTFL).

    ⭐ ATFL: Most commonly injured in ankle sprains (inversion injury). Weakest lateral ligament.

• Subtalar (Talocalcaneal) Joint: Plane; Talus, Calcaneus.
  • Movements: Inversion/Eversion.
  • Ligament: Interosseous talocalcaneal (strongest).
• Midtarsal (Chopart's) Joint: Talonavicular & Calcaneocuboid.
  • Ligament: Bifurcate (Calcaneonavicular, Calcaneocuboid parts).
• Tarsometatarsal (Lisfranc's) Joint Complex:
  • Ligament: Lisfranc (Medial cuneiform to 2nd Met base). Key for midfoot arch.
• Spring Ligament (Plantar Calcaneonavicular): Supports medial arch.

Foot & Ankle Muscles & Tendons - Motion Masters

• Anterior (Dorsiflexion):
  • Tibialis Anterior: Main dorsiflexor, inverts.
  • EHL, EDL: Toe extensors.
• Lateral (Eversion):
  • Peroneus Longus & Brevis: Primary evertors, assist plantarflexion.
• Posterior (Plantarflexion):
  • Superficial: Gastrocnemius, Soleus (Achilles tendon).
  • Deep: Tibialis Posterior (main invertor, arch support), FDL, FHL. 📌 Medial Malleolus (ant→post): Tibialis post., FDL, Artery (post. tibial), Vein, Nerve (tibial), FHL. (Tom, Dick And Very Nervous Harry)

⭐ Thompson test: Squeeze calf; no plantarflexion = Achilles rupture. Often with palpable gap.

Foot & Ankle Neurovascular Supply - Lifeline Network

• Arteries:
  • Anterior Tibial → Dorsalis Pedis (DP). Pulse: lateral to EHL.
  • Posterior Tibial → Medial & Lateral Plantar Arteries. Pulse: posterior to medial malleolus.
    • Plantar arteries + DP branch form Deep Plantar Arch.
• Nerves:
  • Tibial N. → Medial & Lateral Plantar Nerves (sole: sensory/motor).
  • Common Peroneal N.:
    • Deep Peroneal: Ant. compartment motor; 1st web sensory.
    • Superficial Peroneal: Lat. compartment motor; dorsum sensory (most).
  • Sural N.: Lateral foot/heel sensory.
  • Saphenous N.: Medial ankle/foot sensory.

⭐ Tarsal Tunnel Syndrome: Tibial Nerve (or branches) compression under flexor retinaculum, causing pain/paresthesia.

Foot Arches & Biomechanics - Spring in Step

• Three Arches: Medial Longitudinal (MLA), Lateral Longitudinal (LLA), Transverse.
• MLA Support: Tibialis posterior, spring ligament, plantar aponeurosis, FHL.
• Function: Weight bearing, shock absorption, propulsion (windlass mechanism).
• Deformities: Pes planus (fallen MLA), Pes cavus (exaggerated MLA).

⭐ The integrity of the spring ligament (plantar calcaneonavicular ligament) is paramount for static support of the medial longitudinal arch.

High‑Yield Points - ⚡ Biggest Takeaways

• Ankle joint (talocrural): tibia, fibula, talus; main movements are dorsiflexion/plantarflexion.
• Subtalar joint: crucial for inversion and eversion of the foot.
• Medial Deltoid ligament is strong; lateral ATFL is most commonly sprained.
• Tibialis Posterior tendon is key dynamic support for the medial longitudinal arch.
• Lisfranc joint: tarsometatarsal articulation. Chopart joint: talonavicular and calcaneocuboid joints.
• Deep Peroneal nerve injury: foot drop and 1st web space sensory loss.