calcaneus

The calcaneus, or calcaneus bone, is the largest tarsal bone and forms the heel of the foot. It supports most of the body's weight in standing and provides a lever for the gastrocnemius–soleus complex, with the Achilles tendon inserting on its posterior tuberosity.

Anatomy and articulations: The calcaneus has a superior articular surface for the talus, which bears three facets (posterior, middle, and anterior) that contribute to the subtalar joint. Anteriorly, it articulates with the cuboid bone at the calcaneocuboid joint. Medially, the sustentaculum tali projects from the body and supports part of the talus. The posterior aspect presents a large calcaneal tuberosity where the Achilles tendon attaches. The lateral surface provides a pathway for the fibular tendons and related structures, while the plantar surface includes the smooth weight-bearing area.

Function and attachments: The talocalcaneal and calcaneocuboid joints enable hindfoot mobility and stability. The calcaneus acts as a primary weight-bearing element of the hindfoot and serves as the lever arm for plantarflexion. The Achilles tendon inserts at the posterior tuberosity, transmitting muscular force for push-off. Plantar ligaments and intrinsic foot muscles attach to its surfaces, contributing to arch support and foot mechanics.

Clinical significance: Calcaneal fractures typically result from high-energy trauma, such as falls from height, and can involve the subtalar joint, affecting hindfoot alignment and function. Diagnosis relies on radiographs and cross-sectional imaging. Treatment ranges from conservative immobilization to surgical fixation, depending on fracture pattern and joint involvement. Vascular and neural supplies accompany the bone, with arterial input from the posterior tibial and peroneal arteries and innervation via branches of the tibial nerve to the heel region.