Talus (Ankle Bone)
Talus
location_on Between the tibia/fibula above and the calcaneus below, forming the keystone of the ankle
The talus is the second largest tarsal bone and the keystone of the foot, transferring the entire weight of the body from the leg to the foot. It has no muscular attachments, being held in place entirely by ligaments and the bony mortise of the ankle. Approximately 60% of the talus surface is covered by articular cartilage. The talus has a tenuous blood supply, making it highly susceptible to avascular necrosis following fracture.
Key Anatomical Features
- Body (trochlea) is wedge-shaped, wider anteriorly, and sits within the ankle mortise
- Head articulates with the navicular bone anteriorly
- Neck connects the body to the head and is the most common fracture site
- No muscles attach to the talus; it is held in place entirely by ligaments
- Approximately 60% of its surface is covered with articular cartilage
- Lateral process articulates with the fibula and is the site of snowboarder's fracture
Muscle Attachments
| Muscle | Attachment | Action |
|---|---|---|
| No direct muscular attachments | The talus is unique in having no muscular or tendinous insertions | It functions entirely through articular surfaces and ligamentous connections |
| Deltoid ligament (medial) | Medial malleolus to talus body and neck | Stabilizes the ankle against eversion |
| Anterior talofibular ligament | Lateral malleolus to talar neck | Primary restraint against ankle inversion (most commonly injured ankle ligament) |
| Posterior talofibular ligament | Lateral malleolus to posterior talus | Resists posterior displacement of the talus |
Joints and Articulations
| Joint | Type | Connects to |
|---|---|---|
| Ankle (talocrural) joint | Synovial hinge | Tibia and fibula (mortise) |
| Subtalar joint | Synovial plane | Calcaneus |
| Talonavicular joint | Synovial ball-and-socket (part of transverse tarsal joint) | Navicular |
Common Pathologies
Talar neck fracture
Classically from forced dorsiflexion (aviator's fracture from rudder pedal impact). Classified by Hawkins into four types. High rates of avascular necrosis: Type I (0-13%), Type II (20-50%), Type III (80-100%).
Avascular necrosis of talus
The talus has a tenuous blood supply that enters distally; neck fractures can disrupt it. Hawkins sign (subchondral lucency at 6-8 weeks) indicates intact blood supply and is a good prognostic sign.
Osteochondral lesion of talus
Cartilage and subchondral bone damage on the talar dome, typically at the medial or lateral corners. Causes deep ankle pain, swelling, and mechanical symptoms.
Lateral process fracture (snowboarder's fracture)
Fracture of the talar lateral process from forced dorsiflexion and inversion, common in snowboarders. Often misdiagnosed as an ankle sprain.
Clinical Relevance
The anterior talofibular ligament is the most commonly injured ligament in the body (ankle sprains). Talar neck fractures require urgent reduction to restore blood supply and reduce AVN risk. The Hawkins sign (subchondral lucency in the talar dome on AP radiograph at 6-8 weeks post-fracture) indicates that the blood supply is intact and AVN is unlikely. Total talar body replacement with custom 3D-printed implants is an emerging treatment for severe talar AVN.
Development and Ossification
The talus ossifies from a single center appearing around the 6th fetal month. It is one of the earliest tarsal bones to ossify. No secondary ossification centers develop, making the talus entirely ossified from its single center.
Did You Know?
- The talus is one of only two bones in the body with no muscular attachments (the other being the sesamoid bones functionally embedded in tendons)
- Roman soldiers used tali (plural of talus) from sheep as dice for gambling
- Talus means ankle bone in Latin, and is also the root of the word talisman
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