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Interosseous membrane (middle tibiofibular ligament)

The interosseous membrane of the leg, also called the middle tibiofibular ligament, is a strong fibrous sheet connecting the interosseous borders of the tibia and fibula. It runs obliquely downward and laterally from the tibia to the fibula, binding the two bones firmly together while allowing passage of neurovascular structures.

It plays a key role in load sharing, ankle stability, and force transmission between the tibia and fibula. In the lower part of the leg, the membrane is reinforced by the interosseous ligament of the distal tibiofibular syndesmosis, which contributes to ankle stability.

Synonyms

  • Middle tibiofibular ligament

  • Tibiofibular interosseous ligament

  • Interosseous ligament of the leg

Attachments

  • Medially: Sharp interosseous crest of the tibia

  • Laterally: Interosseous border of the fibula

  • Openings:

    • Superior opening near the proximal end for the anterior tibial vessels

    • Inferior opening near the distal end for the perforating branch of the fibular artery

Course

  • Fibers run downward and laterally from the tibia to the fibula

  • Taut throughout the leg, maintaining close approximation of tibia and fibula

  • Provides additional stability to the tibiofibular articulation and ankle mortise

Relations

  • Anteriorly: Tibialis anterior, extensor hallucis longus, extensor digitorum longus, anterior tibial vessels, and deep fibular nerve

  • Posteriorly: Tibialis posterior, flexor hallucis longus, flexor digitorum longus, and posterior tibial vessels

Function

  • Stabilization: Maintains integrity of tibia-fibula relationship during weight bearing

  • Force transmission: Distributes and transfers axial loads between tibia and fibula

  • Muscle attachment: Provides origin sites for tibialis anterior, tibialis posterior, and other deep leg muscles

  • Compartment separation: Separates anterior and posterior compartments of the leg

  • Clinical importance: Supports syndesmotic stability, critical for ankle mechanics

Clinical Significance

  • Syndesmotic injuries ("high ankle sprains"): Involve distal extensions of the interosseous membrane, causing instability of ankle mortise

  • Fractures: Proximal fibular fractures (Maisonneuve injury) may involve disruption of the membrane

  • Chronic exertional compartment syndrome: Membrane may be fenestrated surgically to relieve pressure

  • MRI role: Identifies tears, scarring, or fluid tracking along membrane in trauma

MRI Appearance

  • T1-weighted images:

    • Normal membrane: low signal (dark linear band) between tibia and fibula

    • Muscle attachments appear as intermediate signal

    • Pathology: tears appear as focal discontinuity with adjacent intermediate-to-high signal

  • T2-weighted images:

    • Normal membrane: dark (low signal)

    • Injury: bright hyperintense signal indicating tear, edema, or fluid tracking between tibia and fibula

    • Surrounding muscle edema may accompany acute syndesmotic injury

  • STIR:

    • Normal: dark

    • Pathology: bright hyperintensity where there is edema, hemorrhage, or fluid extravasation

  • Proton Density Fat-Saturated (PD FS):

    • Membrane remains dark linear structure

    • Pathology: bright irregular signal changes showing partial or complete tear

    • Excellent for subtle interosseous membrane disruption and syndesmosis injuries

  • T1 Fat-Sat Post-Contrast:

    • Normal: minimal to no enhancement

    • Tears: perimembranous enhancement indicating inflammation or scarring

    • Chronic changes: fibrotic thickening with variable enhancement

CT Appearance

Non-Contrast CT:

  • Membrane poorly visualized (thin soft-tissue density)

  • Indirect signs: tibia-fibula malalignment, widening of tibiofibular clear space in syndesmotic injury

  • Chronic calcification may rarely be seen along membrane

Post-Contrast CT (standard):

  • Limited role for membrane evaluation

  • Enhancement may occur around torn or inflamed areas, but MRI is superior

MRI images

Interosseous membrane (middle tibiofibular ligament) Axial cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000

MRI images

Interosseous membrane (middle tibiofibular ligament) Axial cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000_00001