calcanei

Calcanei is the plural form of calcaneus, the heel bone of the foot. Each calcaneus is the largest tarsal bone and forms the posterior part of the hindfoot. It bears much of the body’s weight during standing and locomotion and serves as a lever for the gastrocnemius-soleus complex during push-off.

Structure and features: The calcaneus has a substantial body and a prominent posterior tuberosity where the Achilles tendon inserts. On the medial aspect is the sustentaculum tali, a shelf-like projection that supports the talus and provides a passage and shelter for tendons, including the flexor hallucis longus. The superior surface bears multiple articular facets (posterior, middle, and anterior) that articulate with the talus to form the subtalar joint. The inferior (plantar) surface provides attachment sites for the plantar fascia and various ligaments; the lateral surface offers attachments for the ligaments of the lateral ankle.

Articulations: The calcaneus articulates superiorly with the talus to form the subtalar joint and anteriorly with the cuboid bone at the calcaneocuboid joint. The sustentaculum tali acts as a support for the talus and a groove for tendons.

Ligaments and tendons: The Achilles tendon attaches to the posterior tuberosity; the plantar fascia and the long plantar ligament attach to the plantar surface; the spring ligament (calcaneonavicular ligament) connects the calcaneus to the navicular bone via the sustentaculum tali.

Function: The calcanei provide a robust foundation for weight transfer, absorb impact, and enable plantar flexion and push-off during gait.

Clinical notes: Calcaneal fractures often result from high-energy impacts and can affect the subtalar joint. Conditions affecting the heel, such as plantar fasciitis or heel spurs, frequently involve the calcaneus.

Etymology: Calcaneus comes from Latin calx, heel; calcanei is its plural form in Latin.