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.

Region: Lower Leg

Biomechanics

Function & Actions

Divides the posterior leg compartment into superficial and deep components, preventing cross-compartmental pressure equalisation and requiring individual surgical release.

Clinical Relevance

Clinical Notes

Failure to release the transverse intermuscular septum is the most common cause of inadequate fasciotomy in lower leg compartment syndrome. The deep posterior compartment is easily missed when only the superficial posterior is decompressed. The tibial nerve and posterior tibial vessels are deep to this septum and must be protected during release.

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.