Anatomy - Muscular System: Leg and Extrinsic Foot Notes

Lecture Agenda

  • Principles of Movement for the Leg & Extrinsic Foot
  • ‘Geography’ of the Leg & Extrinsic Foot
  • Muscles of the Leg & Extrinsic Foot
    • Origins, Insertions, Paths, Functions
    • Overall Functional Approach

Key Concepts

1. Principles of Movement
  • Flexion and Extension
    • Flexion: Decreasing the angle between limb segments (e.g., thigh and leg at the knee).
    • Extension: Increasing the angle between limb segments.
  • Plantarflexion and Dorsiflexion
    • Plantarflexion: Posterior and inferior rotation of the foot, bringing the plantar surface posteriorly.
    • Dorsiflexion: Superior rotation of the foot, with the dorsum approaching the anterior leg.
  • Inversion and Eversion
    • Inversion: Rotation of the foot so the plantar surface faces medially.
    • Eversion: Rotation of the foot so the plantar surface faces laterally.
2. Geography of the Leg
Compartments of the Leg
  • Anterior Compartment: Contains extensors of the toes and dorsiflexors of the ankle.
  • Posterior Compartment: Contains flexors of the toes and plantarflexors of the ankle.
  • Lateral Compartment: Contains muscles that aid in eversion of the foot.
3. Muscles of the Leg & Extrinsic Foot
Anterior Compartment Muscles
  • Tibialis Anterior: Dorsiflexes and inverts the foot.
  • Origin: Lateral tibial shaft
  • Insertion: Medial cuneiform and base of 1st metatarsal
  • Innervation: Deep fibular nerve.
  • Extensor Digitorum Longus: Extends lateral four toes and dorsiflexes the foot.
  • Origin: Proximal medial fibula and lateral tibial condyle
  • Insertion: Distal and middle phalanges of digits II-V.
  • Innervation: Deep fibular nerve.
  • Extensor Hallucis Longus: Extends the 1st digit and dorsiflexes the foot.
  • Origin: Medial fibula
  • Insertion: Dorsal surface of 1st distal phalanx.
  • Innervation: Deep fibular nerve.
Posterior Compartment Muscles
  • Gastrocnemius: Plantarflexes foot at the ankle and flexes leg at the knee.
  • Origin: Medial and lateral heads from the femoral condyles
  • Insertion: Posterior calcaneus via calcaneal tendon.
  • Innervation: Tibial nerve.
  • Soleus: Primarily plantarflexes the foot
  • Origin: Posterior tibia and fibula
  • Insertion: Posterior calcaneus via calcaneal tendon.
  • Innervation: Tibial nerve.
  • Flexor Digitorum Longus: Flexes lateral four toes and assists in plantarflexion.
  • Origin: Medial posterior tibia
  • Insertion: Plantar surfaces of distal phalanges of toes II-V.
  • Innervation: Tibial nerve.
  • Flexor Hallucis Longus: Flexes the 1st digit and assists in plantarflexion.
  • Origin: Posterior fibula
  • Insertion: Plantar surface of 1st distal phalanx.
  • Innervation: Tibial nerve.
  • Tibialis Posterior: Inverts and plantarflexes the foot.
  • Origin: Posterior tibia and fibula
  • Insertion: Navicular and medial cuneiform.
  • Innervation: Tibial nerve.
Lateral Compartment Muscles
  • Fibularis Longus: Evert the foot and assist in plantarflexion.
  • Origin: Lateral fibula
  • Insertion: Medial cuneiform and base of 1st metatarsal.
  • Innervation: Superficial fibular nerve.
  • Fibularis Brevis: Evert the foot and assist in plantarflexion.
  • Origin: Lateral fibula
  • Insertion: Base of 5th metatarsal.
  • Innervation: Superficial fibular nerve.

Functional Approaches for Each Muscle Group

  • Flexors: Must cross relevant joints on the appropriate side and travel in a proximal-distal direction.
  • Extensors: Similar rules apply as with flexors but focus on increasing joint angles or extending limbs.
  • Clearly identify the functionality of each muscle based on its path and distance from the center of the joint it acts upon.