The talus (also ankle bone, Latin: os talus) is an irregularly shaped tarsal bone that links the foot and the leg through the ankle joint.
The talus articulates not only with the leg bones (tibia and fibula) at the ankle joint, but it also articulates with the calcaneus below and the navicular bone in front, forming the talocalcaneonavicular joint.
The talus has three parts:
- neck, and
- head of the talus.
The head of the talus is a spherical part of the bone directed anteriorly and medially. It has an articulating surface for communication with the navicular bone.
Proximal to the head of the talus is a narrow part called the neck of the talus.
The body of the talus features several landmarks and articulating surfaces, including:
- trochlea of the talus, with three surfaces -
- medial malleolar surface,
- lateral malleolar surface,
- superior articular surface of the talus,
- inferior articular surfaces (anterior, middle, posterior),
- sulcus tali, and
- tarsal sinus (formed together with the calcaneus).
The trochlea of the talus is the larger and posterior part of the body of the talus. It has a semi-cylindrical form and articulates with tibia and fibula. Three surfaces are presenting on the trochlea of the talus: the medial and lateral malleolar surfaces, and the superior articular surface of the talus. The medial malleolar surface is an almost sagittally oriented surface of the talus that articulates with the medial malleolus (tibia). The lateral malleolar surface is a surface on the lateral side of the talus articulating with the lateral malleolus (fibula). The superior articular surface of the talus articulates with the inferior articular surface of the tibia.
There are three inferior articular surfaces (anterior, middle, posterior) found on the inferior side of the talus. These surfaces serve for the attachment of joints connecting the talus with the calcaneus.
The sulcus tali is a groove on the inferior surface of the talus between the posterior and the middle articular surfaces.
The tarsal sinus is an indentation formed by the sulcus tali and the calcaneal sulcus.