Posterior Leg Anatomy Overview

Overview of the Posterior Leg Anatomy

• The posterior leg, or calf, lies between the knee and the ankle.
• Calf anatomy includes multiple layers of muscles, nerves, arteries, and veins.
• A 100km ultra-marathon from Bath to Chilcompton is planned to raise money for Macmillan Cancer Support.
• Donations can be made via a Just Giving page (link in description).

Anatomical Terminology

• The model is of a left leg.
• The big toe is the great toe or hallux.
• Structures related to the big toe are "hallucis."
• Medial is the side of the leg where the big toe is.
• Lateral is the side of the leg where the little toe is.
• Leg is the region between the knee and the ankle.
• The lower limb is compartmentalized by fascia, with focus on the posterior compartment.

Superficial Structures

• The small (or short) saphenous vein runs along the posterior calf as a superficial vein.
• The small saphenous vein drains into deeper veins near the popliteal fossa.
• Calf varicose veins often stem from issues in the small saphenous vein's valves.
• The sural nerve accompanies the small saphenous vein, providing cutaneous innervation.
• The sural nerve innervates the lateral ankle and foot skin.

Superficial Muscles

• The gastrocnemius is the most prominent calf muscle, featuring lateral and medial heads.
• The gastrocnemius heads connect to the femur's lateral and medial condyles.
• The calcaneal tendon (Achilles tendon) comprises the tendons of the gastrocnemius, soleus, and plantaris muscles.
• The Achilles tendon is often injured by runners.
• The soleus muscle is located under the gastrocnemius.
• The soleus originates from the tibia and fibula.
• The gastrocnemius spans the knee and ankle joints.
• The soleus only spans the ankle joint.
• The gastrocnemius and soleus facilitate plantar flexion.
• The plantaris is a small muscle in the posterior leg's superficial layer.
• The plantaris crosses both the knee and ankle joints.
• The tibial nerve innervates all three superficial muscles.

Nerves

• The sciatic nerve splits into the tibial and common fibular nerves.
• The tibial nerve runs through the popliteal fossa, innervating all posterior leg muscles.
• The sural nerve branches from the tibial nerve, emerging between the heads of the gastrocnemius.

Deep Layer of Muscles

• The deep calf layer contains four muscles: popliteus, flexor hallucis longus, flexor digitorum longus, and tibialis posterior.
• The popliteus unlocks the knee joint and starts knee flexion.
• The popliteus runs from the tibia to the lateral femoral condyle.
• The flexor hallucis longus flexes the big toe.
• The flexor digitorum longus flexes the other four toes.
• Tibialis posterior is the third muscle in the deep layer.
• The flexor hallucis longus primarily attaches to the fibula.
• The flexor digitorum longus primarily attaches to the tibia.
• The tibialis posterior attaches to both the tibia and fibula, and the interosseous membrane.
• The tendons of these three muscles curve medially around the medial malleolus of the tibia.
• The tibialis posterior inserts into the medial foot bones, providing foot stabilization and inversion.
• Eccentric loading of the tibialis posterior supports the medial arch during walking and running.

Arteries and Veins

• Deep veins are in the lower limb, blood clots can form if venous blood flow is impaired.
• The popliteal artery, from the femoral artery, traverses the popliteal fossa.
• The popliteal artery branches into the anterior tibial artery and the tibioperoneal trunk.
• The anterior tibial artery moves to the leg's anterior compartment.
• The tibioperoneal trunk divides into the fibular and posterior tibial arteries.
• The fibular artery runs laterally to the fibula.
• The posterior tibial artery descends the leg and passes behind the medial malleolus.