Transverse Intermuscular Septum of the Leg

septum intermusculare transversum cruris

The transverse intermuscular septum (deep transverse fascia) of the leg divides the posterior compartment into superficial (gastrocnemius, soleus, plantaris) and deep (tibialis posterior, flexor digitorum longus, flexor hallucis longus) components. It is the critical structure separating the two posterior compartments in fasciotomy.

Anatomical Data

Boundaries & Contents

Location	Back of the leg, between the superficial and deep posterior muscle groups
Boundaries	Attached medially to the medial border of the tibia Attached laterally to the posterior border of the fibula Thickens near the ankle and joins the flexor retinaculum
Contents	Covers the posterior tibial vessels and tibial nerve, which run deep to it

Biomechanics

Function & Actions

Divides the posterior compartment into superficial (gastrocnemius, soleus, plantaris) and deep (popliteus, tibialis posterior, flexor digitorum longus, flexor hallucis longus) compartments, which must both be opened in fasciotomy.

Clinical Relevance

Clinical Notes

Failure to release the transverse intermuscular septum is the most common cause of inadequate fasciotomy in lower leg compartment syndrome, because the deep posterior compartment is easily missed when only the superficial posterior fascia is opened. The tibial nerve and posterior tibial vessels lie deep to this septum and must be protected during release. In chronic exertional compartment syndrome confined to the deep posterior compartment, isolated release of this septum through a medial approach can be curative. Its attachment along the posteromedial tibia lies close to the area involved in medial tibial stress syndrome (shin splints).

Pathology

Common Injuries & Conditions

Missed Deep Posterior Compartment Syndrome

Persistent ischaemia of the deep posterior compartment due to failure to release the transverse intermuscular septum during fasciotomy, producing tibialis posterior and toe flexor necrosis.

Explore

More in Lower Leg

Browse all of Lower Leg →