Anatomy of the Back of the Leg

Overview

• The anatomy of the back of the leg includes muscles divided into two groups: superficial and deep.
• Focus is primarily on muscles, nerves, and blood supply.

Superficial Group Muscles

Gastrocnemius Muscle

• Characteristics: Two heads - medial and lateral.
• Origin:
  • Medial head: Arises from the posterior superior aspect of the medial femoral condyle.
  • Lateral head: Arises from the lateral surface above the lateral femoral condyle.
• Insertion: Unites with soleus tendon to form the tendo calcaneus, inserting into the calcaneum.
• Innervation: Supplied by the tibial nerve.
• Function: Powerful plantar flexor of the foot, flexes knee joint.
• Shape: Belly-like, hence 'gastrocnemius'.

Plantaris Muscle

• Characteristics: Small belly and long tendon.
• Insertion: Tendon passes between gastrocnemius and soleus, inserts near the tendon calcaneus.
• Function: Weak plantar flexor.
• Innervation: Tibial nerve.

Soleus Muscle

• Characteristics: Flat and broad, resembling a sole.
• Origin: From tibia (soleal line) and fibula.
• Insertion: Forms tendon calcaneus with gastrocnemius.
• Function: Strong, slow plantar flexor.
• Differences with Gastrocnemius: More powerful, acts as 'bottom gear' during strolling.

Deep Group Muscles

Popliteus Muscle

• Origin: From lateral femoral condyle.
• Insertion: Into triangular area above the soleal line.
• Function: Unlocks knee joint.
• Innervation: Tibial nerve.

Tibialis Posterior Muscle

• Origin: Posterior surfaces of tibia and fibula.
• Insertion: Navicular bone and tarsal/metatarsal bones.
• Function: Inverts foot, maintains medial longitudinal arch.

Flexor Digitorum Longus

• Origin: Upper two-thirds of the medial part of tibia.
• Insertion: Plantar surface of distal phalanges.

Flexor Hallucis Longus

• Origin: Lower three-fourths of posterior fibula.
• Insertion: Base of distal phalanx of great toe.

Retinaculum and Related Structures

Flexor Retinaculum

• Attachments: Between medial malleolus and calcaneum.
• Contents: Tendons and neurovascular structures, arranged medially to laterally.

Nerve and Blood Supply

Tibial Nerve

• Origin: Terminal branch of the sciatic nerve.
• Function: Supplies all leg muscles, articular branches to ankle joint, cutaneous branches for heel.

Posterior Tibial Artery

• Origin: From the popliteal artery.
• Branches: Circumflex fibular artery, peroneal artery, nutrient artery to tibia.
• Function: Supplies blood to posterior compartment of the leg.

Summary

• The posterior leg contains critical muscles for movement and balance, all primarily supplied by the tibial nerve.
• Key functions include plantar flexion, inversion, and support of the foot's arches. Understanding the anatomy is crucial for diagnosing leg injuries and conditions.