Foot & ankle

Anatomy of the Foot and Ankle

• The foot and ankle are composed of 7 tarsal bones, 5 metatarsal bones, and 14 phalanges.
• The metatarsals and phalanges are organized similarly to the metacarpals and phalanges of the hand.
• The tarsal bones are short bones arranged in three rows: proximal, middle, and distal.
  • Proximal row: talus and calcaneus.
  • Middle row: navicular.
  • Distal row: three cuneiforms (medial, intermediate, and lateral) and cuboid.
• The talus is the second largest bone in the foot, lying above the calcaneus (heel bone).
• The calcaneus is the largest bone in the foot.
• The navicular bone is boat-shaped and lies in front of the talus.
• The cuboid bone is cubical and lies in front of the lateral part of the calcaneus.
• The cuneiform bones are wedge-shaped and arranged from side to side in front of the navicular.
• The metatarsals are miniature long bones numbered 1-5 from medial to lateral. Each consists of three parts: a distal end (head), a shaft (body), and a proximal end (base).
• The phalanges are miniature long bones forming the toes. The great toe has two phalanges, and the other toes have three phalanges each (proximal, middle, and distal).
• The foot has longitudinal and transverse arches that help protect soft tissue and convert elastic energy during movement.

Learning Outcomes

• Identify and describe the bones (and bony features) of the ankle joint and foot.
• Identify and describe the major joints of the ankle and foot and discuss their actions.
• Summarize the compartments of the foot and discuss the muscles and their actions within each compartment.
• Review the course and distribution of the main neurovascular structures of the ankle and foot.
• Discuss the functions of ligaments associated with the ankle joint and foot.
• Describe the anatomy of the arches of the foot.
• Discuss the tarsal tunnel and the relationship of neurovascular structures passing through it.
• Apply anatomical knowledge to clinical problems of the ankle and foot (e.g., Pott's fracture, ankle sprains, foot amputations, plantar fasciitis).

Joints of the Foot

• The joints of the foot form a functional unit for ambulation.
• Key joints include:
  • Ankle joint (talocrural)
  • Subtalar/talocalcaneal
  • Talocalcaneonavicular
  • Calcaneocuboid
  • Cuneonavicular
  • Cuneocuboid
  • Intercuneiform
  • Tarsometatarsal
  • Intermetatarsal
  • Metatarsophalangeal
  • Interphalangeal
• Chopart's joint (transverse tarsal) and Lisfranc's joint (tarsometatarsal and intermetatarsal joints) are also important.

Ankle Joint

• The ankle joint is a compound joint consisting of the tibia, fibula, and talus.
• Its shape is trochlear.
  • The proximal articular surface is formed by the lower end of the tibia (including the medial malleolus), the lateral malleolus, and the inferior transverse tibiofibular ligament to create a deep tibiofibular socket.
  • The distal articular surface is formed by the articular facets on the upper, medial, and lateral aspects of the talus.
• The ankle joint has collateral ligaments: medial (deltoid) and lateral ligaments (anterior talofibular, posterior talofibular, and calcaneofibular) that provide stability.

Tarsal Tunnel

• A space behind the medial malleolus.
• Contains structures like tibial nerve, posterior tibial vessels and tendons of flexor digitorum longus and hallucis longus, and tibialis posterior tendon.

Muscles

• Foot muscles are classified as extrinsic (originate outside the foot) and intrinsic (originate within the foot).
• Extrinsic muscles act on the foot, causing plantarflexion, dorsiflexion, eversion, and inversion.
• Intrinsic muscles control the finer movements of individual toes.
• Specific muscles include extensor digitorum brevis, extensor hallucis brevis, abductor hallucis, abductor digiti minimi, flexor digitorum brevis, flexor hallucis brevis, adductor hallucis, and the interossei muscles (both dorsal and plantar).

Arterial Supply

• The foot's arterial supply comes from the anterior tibial artery (dorsalis pedis) and posterior tibial artery.
  • Branches supply the foot's dorsal and plantar surfaces.

Venous Drainage

• Superficial veins (dorsal venous arch): drain into the medial and lateral marginal veins.
• Deep veins (plantar venous arch): drain into the medial and lateral plantar veins, which then drain into the posterior tibial vein.

Nerves

• The foot's nerves come from the tibial, deep fibular, superficial fibular, sural, and saphenous nerves.
• Tibial nerve branches into medial and lateral plantar nerves, supplying sensory and motor functions.

Clinical Correlations

• Common conditions include:
  • Pes planus (flat feet) - loss of medial longitudinal arch
  • Ankle sprains (inversions/eversions)
  • Pott's fracture (fracture dislocation of the ankle)
  • Plantar fasciitis (inflammation of plantar aponeurosis)

Amputations

• Severance of a body part due to gangrene, peripheral arterial disease, infection, malignancy, irreparable trauma, compartment syndrome, severe burns, contractures, anomalies or severe thermal/electrical injury are indications for amputation.