What is the Talus Bone
Talus bone, also known as the ankle bone or astragalus, is the second-largest tarsal bone that links the leg to the foot by forming the ankle joint. This small, irregular, saddle-shaped bone derives its name from the Latin word ‘taxillus’, meaning a ‘small die or cube’, as this bone from horses was used to make dice for various games of chance by Roman soldiers.
Where is the Talus Located
The Talus is located in the hindfoot region, between the heel bone (calcaneus) and the tibia and fibula of the lower leg.
Quick Facts
| Type | Short bone |
|---|---|
| Length and Width | Approximately 65.15 mm Approximately 48.4 mm |
| How many are there in the human body | 2 (1 in each foot) |
| Articulates with | Four bones: the tibia, fibula, calcaneus, and navicular |
Functions
- The talus serves as the primary connection between the foot and leg, forming the ankle joint.
- It enables the surrounding bones of the ankle to move in various directions while supporting the body’s weight.
- Its main function is to transfer body weight from the tibia to the heel bone (calcaneus), thus enabling a person to maintain balance while walking.
- It absorbs additional force when the foot twists or sudden weight is applied, especially in the ankle region.
Structure and Anatomy
As described, this is a small, irregular, saddle-shaped bone, which can be divided into three parts: head, neck, and body. The talus also has several joint surfaces and two protrusions on the back and side, the posterior and lateral processes. It is wider in the front than in the back. Two-thirds of it remains covered with cartilage to help cushion its movements as part of the ankle and the foot.
Bony Landmarks
Head
The part of the talus that lies toward the toe is called the talar head. It is large, oval, and has a convex anterior surface for articulating with the navicular bone. Its lower side bears three joint areas, separated by smooth ridges.
The head has medial and lateral facets for articulation with the calcaneum. The medial joint surface is convex and triangular or semi-oval in shape, while the lateral, also known as the anterior calcaneal articular surface, is slightly flattened. Between these two facets, there is another one through which the plantar calcaneonavicular ligament or spring ligament runs.
Neck
The neck of the talus is the constricted region between the oval head and body. It has several rough surfaces for ligament attachment. Its lower surface contains a deep groove, the sulcus tali, which forms the roof of the sinus tarsi upon articulating with the calcaneus. The sinus tarsi is a small tunnel located between the talus and calcaneus bones, containing numerous ligaments and a joint capsule. At the back of the sulcus tali is a large facet that articulates with the calcaneus.
The relatively thin diameter of the neck makes it a weaker area and hence more susceptible to fractures.
Body
The cuboid body of the talus comprises most of its volume. It has five surfaces: superior, inferior, medial, lateral, and posterior.
The superior surface, also known as the trochlear surface or talar dome, is curved and smooth. This part of the bone articulates with the tibia of the lower leg. It is covered with hyaline cartilage, convex from front to back, slightly concave from side to side, and wider in the front than behind.
The medial surface has a pear-shaped joint facet for the tibial end (the medial malleolus), in continuation with the trochlear surface. Below the joint surface, there is a rough depression for ligament attachment of the deltoid ligament.
The lateral surface has a large triangular concave facet for articulating with the lower end of the fibula (the lateral malleolus). The front half is continuous with the trochlear surface and has a rough depression for the attachment of the anterior talofibular ligament. The lower part of this surface forms a bony projection called the lateral process that supports the lower portion of the lateral joint facet.
The posterior surface has a posterior process with a lateral and medial tubercle separated by a groove through which the tendon of flexor hallucis longus runs.
Articulations
Ankle joint or talocrural joint: It is a hinge joint, where the talus articulates with the leg bones, tibia, and fibula.
Talocalcaneonavicular joint: The following two synovial ball and socket joints are collectively known as the talocalceneonavicular joint.
- Subtalar or talocalcaneal joint: Here, the talus joins the heel bone below.
- Talonavicular joint: Here, the talus joins the navicular in front.
Ligament Attachments
While no muscles are connected to the talus, multiple ligaments are attached to this bone. These ligaments ensure that the talus cannot sway from side to side or move backward or forward relative to the tibia and fibula.
On the sides, the ankle joint is held together by the posterior talofibular and anterior talofibular ligaments. From the center, it is held together by a massive ligament, the deltoid ligament.
All the ligaments attached to the talus are listed below:
- Anterior talofibular ligament
- Posterior talofibular ligament
- Talocalcaneal ligaments
- Tarsal sinus ligaments
- Cervical ligament
- Talocalcaneal interosseous ligament
- Deltoid ligament
- Anterior tibiotalar ligament
- Posterior superficial tibiotalar ligament
- Posterior deep tibiotalar ligament
- Dorsal talonavicular ligament
FAQs
Q.1. Is the talus a weight-bearing bone?
Ans. No, the talus is not a weight-bearing bone. It transmits the entire body weight to the foot.
References
- Talus – Kenhub.com
- Talus – Radiopaedia.org
- Anatomy of the Talus Bone – Study.com
- Talus – Sciencedirect.com
- Anatomy, Bony Pelvis and Lower Limb, Foot Talus – Ncbi.nlm.nih.gov
- Bones of the Foot: Tarsals, Metatarsals and Phalanges – Teachmeanatomy.info
