Posterior Intermuscular Septum of the Leg

septum intermusculare cruris posterius

The posterior intermuscular septum of the leg separates the lateral (peroneal) compartment from the superficial posterior compartment, running from the posterior fibula to the crural fascia. It defines the posterior boundary of the lateral compartment and the lateral boundary of the superficial posterior compartment.

Anatomical Data

Boundaries & Contents

Location	Lateral side of the leg, between the lateral and posterior compartments
Boundaries	Attached to the posterior border of the fibula Continuous with the deep surface of the crural fascia

Biomechanics

Function & Actions

Separates the lateral (fibular) compartment from the superficial posterior compartment and gives partial origin to fibularis longus and soleus.

Clinical Relevance

Clinical Notes

The posterior intermuscular septum is released during the lateral incision in two-incision fasciotomy for lower leg compartment syndrome, decompressing both the lateral and superficial posterior compartments. It is also the boundary for peroneal flap elevation. The short saphenous vein and sural nerve pass near its posterior extent.

Pathology

Common Injuries & Conditions

Lateral-Posterior Compartment Release

Incision through the posterior intermuscular septum during lateral fasciotomy to decompress both the peroneal and superficial posterior compartments simultaneously.

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