Calcaneus

Where is the calcaneus?

The calcaneus lies in the hindfoot, below the talus and behind the midfoot. Its long axis runs about along the midline of the foot. (StatPearls, Calcaneus)

In front, the cuboid bone articulates with it. (OpenStax A&P 2e, 8.4; StatPearls, Calcaneus; Gray’s Anatomy (1918), Calcaneus, p. 263)

What are the parts of the calcaneus?

Low on its back is the calcaneal tuberosity. On its lateral surface, the fibular trochlea separates the tendon of fibularis brevis, which passes above it, from that of fibularis longus below. (StatPearls, Calcaneus)

On its medial surface, the sustentaculum tali juts out to support the talus, and a groove beneath it carries the tendon of flexor hallucis longus. (OpenStax A&P 2e, 8.4; StatPearls, Calcaneus)

Grooves on the calcaneus and talus meet to form the tarsal sinus, a space between the two bones that holds vessels, nerves, ligaments and fat. (StatPearls, Calcaneus)

Which joints and tendons does the calcaneus have?

Its upper surface carries the anterior and posterior talar facets, and the sustentaculum tali carries the middle one; all three meet the talus. The anterior and middle facets also take part, with the head of the talus and the navicular bone, in the talocalcaneonavicular joint. Its front face carries the facet for the calcaneocuboid joint. (StatPearls, Calcaneus and Navicular Bone)

The gastrocnemius, soleus and plantaris join in the calcaneal (Achilles) tendon, which inserts on the calcaneus. (OpenStax A&P 2e, 11.6; StatPearls, Calcaneus)

The plantar aponeurosis runs from the calcaneus to the toes and keeps the longitudinal arch from collapsing under body weight. On the lateral side of the ankle, the calcaneofibular ligament ties it to the fibula. (OpenStax A&P 2e, 11.6 and 9.6; StatPearls, Foot Fascia and Ankle Joint)

What does the calcaneus do?

Body weight passes from the tibia through the talus to the calcaneus, which rests on the ground. At the back of the longitudinal arches, it is the support where the arches meet the ground. (OpenStax A&P 2e, 8.4; Gray’s Anatomy (1918), Calcaneus, p. 263; StatPearls, Foot Talus and Arches of the Foot)

It anchors the Achilles tendon, through which the gastrocnemius, soleus and plantaris plantar flex the foot in standing, walking, running and jumping. Muscles that move the toes attach to it too. (StatPearls, Calcaneus)

How often does the calcaneus break?

The calcaneus is the tarsal bone that breaks most often: StatPearls gives it 60% of tarsal fractures and names falls from a height and road accidents as the main causes. (StatPearls, Calcaneus)

Rare extra ossicles can form near it: the os sustentaculi behind the sustentaculum tali, and the os calcaneus secundarius between the calcaneus, cuboid, talus and navicular. (StatPearls, Calcaneus)

Where the sources differ

OpenStax gives dorsiflexion and plantar flexion to the ankle joint and inversion and eversion to the subtalar joint. StatPearls lists all four movements for the subtalar joint. (OpenStax A&P 2e, 9.6; StatPearls, Calcaneus)

StatPearls’ Calcaneus article names the joint through all three talar facets the talocalcaneal, or subtalar, joint. Its Navicular Bone article treats the talocalcaneonavicular joint and the posterior talocalcaneal joint as two joints that together form the subtalar articular complex. (StatPearls, Calcaneus and Navicular Bone)