Topics

Topic

design image
Talus

The talus is a tarsal bone of the ankle that transmits body weight from the tibia to the foot. It occupies a central position between the leg and foot, articulating with the tibia, fibula, calcaneus, and navicular bones. Unlike most bones, the talus has no direct muscular or tendinous attachments, making it dependent on surrounding ligaments and articular surfaces for stability. Its vascular supply is relatively precarious, which predisposes it to avascular necrosis following fractures or dislocations.

The talus forms the ankle (talocrural) joint, subtalar joint, and talonavicular joint, playing a critical role in ankle mobility, stability, and load transmission.

Synonyms

  • Astragalus

  • Ankle bone

Parts

  • Head: Rounded anterior portion articulating with the navicular and supported by the calcaneus

  • Neck: Constricted part between head and body, vulnerable in talar neck fractures

  • Body: Large posterior portion forming most of the talocrural articulation

  • Talar dome (trochlea): Superior articular surface for tibia and fibula

  • Posterior process: Contains medial and lateral tubercles; groove for flexor hallucis longus tendon

Articulations

  • Superiorly: Tibia (talocrural joint)

  • Laterally: Fibula (talocrural joint)

  • Inferiorly: Calcaneus (subtalar joint)

  • Anteriorly: Navicular (talonavicular joint)

Ligament Attachments

  • Medially: Deltoid ligament (tibiotalar part) attaches to body of talus

  • Laterally: Anterior talofibular ligament, posterior talofibular ligament, and calcaneofibular ligament (ankle stabilizers)

  • Inferiorly: Interosseous talocalcaneal ligament (subtalar joint)

  • Posteriorly: Posterior talotibial ligament, posterior talocalcaneal ligament

Tendon and Muscle Relations

The talus has no direct tendon or muscle attachments, but tendons pass closely around it:

  • Medial side: Tibialis posterior, flexor digitorum longus, flexor hallucis longus (posteromedial groove)

  • Lateral side: Peroneal (fibularis) tendons (posterior to lateral malleolus)

  • Posterior groove: Flexor hallucis longus tendon runs between talar tubercles

Arterial Supply

  • Posterior tibial artery branches: Artery of tarsal canal, deltoid branch, calcaneal branches

  • Dorsalis pedis artery: Artery of sinus tarsi

  • Peroneal (fibular) artery branches contribute minor supply

  • Vascular supply is retrograde and limited, making talar fractures highly prone to avascular necrosis (AVN)

Venous Drainage

  • Venous plexus drains into the posterior tibial vein and fibular vein

Nerve Supply

  • Deep peroneal nerve: Supplies talonavicular and talocrural joints

  • Tibial nerve branches: Supply subtalar and talocrural joints

  • Sural nerve contributions: Supply subtalar joint capsule

Function

  • Weight transmission: Transfers body weight from tibia to calcaneus and foot

  • Stability: Maintains integrity of ankle and hindfoot joints

  • Mobility: Enables dorsiflexion, plantarflexion, inversion, and eversion of the ankle-foot complex

  • Shock absorption: Works with subtalar joint for distributing forces during gait

Clinical Significance

  • Fractures: Talar neck fractures are common and often complicated by avascular necrosis

  • Dislocations: Can occur with high-energy trauma, impairing blood supply

  • Osteochondral lesions (talar dome): Cause chronic ankle pain and instability

  • Avascular necrosis: Due to fragile blood supply, especially after neck and body fractures

  • Imaging relevance: MRI crucial for AVN and osteochondral lesions; CT essential for fracture classification

MRI Appearance

  • T1-weighted images:

    • Normal talar marrow shows intermediate-to-high signal depending on fat content

    • Fracture lines: low-signal linear defects

    • Osteonecrosis: diffuse low signal in talar dome or body

  • T2-weighted images:

    • Marrow signal variable, from intermediate to high depending on fat content

    • Bone marrow edema: bright hyperintense signal

    • Osteochondral lesions: focal areas of high signal intensity with overlying cartilage defect

  • STIR:

    • Normal marrow: suppressed dark

    • Pathology: edema, fractures, or AVN appear bright hyperintense

  • Proton Density Fat-Saturated (PD FS):

    • Normal: uniform low-intermediate signal

    • Pathology: fractures, cartilage defects, and osteonecrosis appear as bright signal abnormalities

  • T1 Fat-Sat Post-Contrast:

    • Normal: homogeneous minimal enhancement

    • Osteonecrosis: lack of enhancement in necrotic area with peripheral rim enhancement

MRI Arthrogram Appearance

  • Contrast outlines talocrural and subtalar joint spaces

  • Osteochondral lesions: contrast pools into defect at talar dome

  • Differentiates stable cartilage fissures from full-thickness defects

CT Appearance

Non-Contrast CT:

  • Provides excellent cortical bone detail

  • Fractures: clearly delineated, especially talar neck/body fractures

  • Osteochondral defects: subchondral bone irregularities visible

  • Avascular necrosis: collapse and sclerosis in chronic cases

Post-Contrast CT (standard):

  • Rarely used for bone directly

  • May highlight peritalar soft tissue pathology

CT Arthrogram Appearance

  • Contrast fills joint surfaces around talus

  • Osteochondral lesions: contrast penetration into subchondral bone defect

  • Useful when MRI contraindicated, particularly for cartilage evaluation

CT VRT 3D image

Talus bone 3d image ct

MRI image

Talus coronal MRI cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000

MRI image

Talus sag MRI cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000

CT image

Talus sag CT cross sectional anatomy radiology image-img-00000-00000