Calcaneus

At a glance

English

Calcaneus

Latin (TA2)

Calcaneus

System

Bone

Region

Foot

Side

Paired, left and right

Series

Tarsal bones

About the calcaneus

The calcaneus is the heel bone and the biggest bone in the foot. It lies under the talus, makes the back of the foot and projects behind the ankle to form the heel. It is a long, roughly box-shaped bone with six surfaces. Its back half, the tuberosity, is the part that meets the ground and carries the Achilles tendon, while the front half supports the talus above and meets the cuboid in front.

The upper surface carries three facets for the talus: a large convex posterior facet and smaller middle and anterior facets. Between the posterior and middle facets runs the calcaneal sulcus, which lies under the matching groove on the talus to form the tarsal canal and its wide outer opening, the tarsal sinus. The middle facet sits on a shelf of bone, the sustentaculum tali, which juts inwards from the medial surface; it holds up the head of the talus, has a groove underneath for the flexor hallucis longus tendon, and gives attachment to the spring ligament and part of the deltoid ligament. The front surface is a saddle-shaped facet for the cuboid at the calcaneocuboid joint.

The back surface is smooth above, where a bursa lies, and roughened in its middle for the Achilles tendon, the shared tendon of gastrocnemius and soleus; plantaris also ends here. The lower surface ends behind in medial and lateral processes that anchor the short muscles of the sole and the plantar aponeurosis, and in front in a small tubercle for the short plantar ligament. On the outer surface a small ridge, the fibular trochlea, separates the tendons of fibularis brevis above and fibularis longus below.

The tibia normally stands straight above the calcaneus, and the line between them is used to judge whether the heel turns in or out. A fall from a height onto the heels can burst the bone, often into the subtalar joint; such fractures are disabling and may come with injuries of the spine. Pain under the heel at the medial process is typical of plantar fasciitis, and a bony bar between the sustentaculum and the talus, a tarsal coalition, can cause a stiff, painful flat foot in adolescents.

Function and supply

Function

Forms the back pillar of the arches of the foot and a lever for the calf muscles, which pull on it through the Achilles tendon to raise the heel in walking, running and jumping.

Nerve supply

Not innervated as a muscle is; the skin of the heel is supplied by medial calcaneal branches of the tibial nerve and by the sural nerve, and the joints by tibial, deep fibular and sural branches.

Blood supply

Medial calcaneal branches of the posterior tibial artery, lateral calcaneal branches of the fibular artery, and the plantar arteries.