posterior leg

EXTREMITY ANATOMY

Posterior Leg Compartment

• All muscles in this compartment are innervated by the tibial nerve.

Posterior Compartment

• The posterior compartment consists of the following structures:
    - Tibialis posterior (TP)
    - Flexor digitorum longus (FDL)
    - Flexor hallucis longus (FHL)
    - Plantaris
    - Gastrocnemius
    - Soleus

Associated Nerves and Blood Vessels

• The posterior compartment is supplied by the posterior tibial vessels and the tibial nerve (TV).

Intermuscular Septa

• The compartment is divided by:
    - Anterior intermuscular septum of the leg (AC)
    - Posterior intermuscular septum of the leg (PC)
    - Transverse intermuscular septum

Superficial - Posterior Compartment

• Includes the following major muscles:
    - Gastrocnemius
    - Soleus
    - Plantaris

• Function:
    - These muscles work together to elevate the heel.
    - They generate approximately 93% of the plantarflexion of the ankle joint.

• Anatomy:
    - The gastrocnemius has two heads, contributing to its function in plantarflexion.
    - The calcaneal tendon (Achilles tendon) is crucial for these movements.

Gastrocnemius

• Two actions of the gastrocnemius are crucial but cannot occur simultaneously:
    - When the knee is flexed, plantarflexion is minimized.
    - When plantar flexed, knee flexion is impaired (active insufficiency).

• Pathology:
    - Tendonitis of the calcaneal tendon may occur due to inflammation from activities like running or walking on uneven surfaces.
    - Repetitive trauma during heel strikes can lead to tendon rupture.

Soleus

• Function:
    - When the foot is planted, the direction of soleal fibers pulls the leg bones posteriorly.
    - This action counteracts the pull of the center of gravity as it passes anterior to the leg bone axis.

• The soleus works alongside the gastrocnemius to stabilize the leg and aid in balance.

Deep - Posterior Compartment

• Includes:
    - Popliteus
    - Flexor digitorum longus (FDL)
    - Flexor hallucis longus (FHL)
    - Tibialis posterior (TP)

• Innervation:
    - All muscles are innervated by the tibial nerve.

Flexor Digitorum Longus

• The action of the FDL is enhanced by the quadratus plantae muscle, which helps reduce diagonal pull by attaching to the posterior aspect of FDL tendons.

• Anatomy components include:
    - Tibialis posterior (TP) tendon
    - Flexor hallucis longus (FHL) tendon
    - Calcaneal tendon
    - Fibularis longus and brevis

Posterior Tibial and Fibular Arteries

• Important branches:
    - Peroneal (fibular) artery
    - Posterior tibial artery
    - Anterior tibial artery
    - Dorsalis pedis artery

• Arteries serve various foot structures:
    - Medial and lateral plantar arteries
    - Calcaneal branches of both the posterior tibial and lateral plantar arteries

Tibial Nerve

• Roots: L4-5, S1-3

• Anatomy:
    - The tibial nerve is the larger terminal branch of the sciatic nerve.
    - It runs through the popliteal fossa alongside the popliteal artery and vein.

• Innervation:
    - Supplies all muscles of the posterior compartment.
    - At the ankle, it lies between FHL and FDL, branching into medial and lateral plantar nerves below the medial malleolus.

Flexor and Extensor Retinacula

• Flexor Retinaculum:
    - Covers structures passing posterior to the medial malleolus.

• Extensor Retinacula:
    - Covers structures passing anterior to the ankle; includes superior and inferior bands.

• Peroneal Retinaculum:
    - Covers structures that pass posterior to the lateral malleolus.

Summary

• The posterior compartment of the leg is vital for propulsion, stabilization, and overall locomotion.

• Understanding the anatomy of the tibial nerve and associated muscles is crucial for assessing injuries and planning rehabilitation.

• The integration of muscular and neural anatomy supports efficient lower limb function, especially during dynamic activities like running and jumping.