The calcaneus (Latin: calcaneus, calcaneum, meaning “heel”) is the sizeable bone forming the heel. It is the largest bone of the foot. The calcaneus articulates with both the cuboid bone and talus within the tarsus.
The calcaneus acts as a short lever for the calf muscles, which insert into its posterior surface via the Achilles tendon. It also provides attachment for other muscles and ligaments and participates in weight-bearing and stability.
There are several essential anatomical landmarks on the surface of the calcaneus, including:
- calcaneal tuberosity,
- calcaneal sulcus,
- sustentaculum tali,
- tarsal sinus (formed together with the talus).
The calcaneal tuberosity is the posterior thickened part of the calcaneus, the half of the bone closest to the heel. This tuberosity serves as the origin site for the abductor hallucis and abductor digiti minimi.
The calcaneal sulcus is a groove between the superior articular surfaces of the calcaneus. With a corresponding groove on the talus (sulcus tali), it forms the tarsal sinus. The calcaneal sulcus provides attachments for the following structures:
- interosseous ligaments,
- talocalcaneal ligaments,
- cervical ligaments, and
- medial root of the inferior extensor retinaculum.
The tarsal sinus opens medially, superior to the sustentaculum tali of the calcaneus, as a funnel-shaped tarsal canal. It contains blood vessels, nerves, fat, and ligaments.
The sustentaculum tali (or the talar shelf) is a horizontal shelf that arises the anteromedial part of the calcaneus. It gives attachment to the plantar calcaneonavicular ligament, tibiocalcaneal ligament, and medial talocalcaneal ligament.
The calcaneus has four articular surfaces, which include:
- superior articular surfaces (anterior, middle, posterior),
- anterior articular surface.
There are three superior articular surfaces on the calcaneus (anterior, middle, posterior). These are the surfaces for articulation with the talus.
The anterior articular surface of the calcaneus is the surface that articulates with the cuboid bone.
There is a rough area located on the superior side of the calcaneus at the back of the heel, where the Achilles tendon inserts. This tendon, as well as other ligaments and muscles, is allows standing and walking. Therefore, if the calcaneus is fractured, it will cause difficulty in standing and walking.