The calcaneus is the primary weight-bearing bone in the heel. Calcaneal fractures are the most frequent tarsal fractures accounting for 2% of all adult fractures and 60% of tarsal fractures. The complex anatomy of the calcaneus should be well understood for determining fracture patterns and accessing calcaneal injuries.

The calcaneus has four articulating surfaces, three superior and one anterior. The superior surfaces containing the posterior, middle and anterior facets, articulate with the talus. The posterior facet is separated from the middle and anterior facets by a groove that runs posteromedially, known as the calcaneal sulcus. The canal formed between the calcaneal sulcus and the talus is called the sinus tarsi. The middle calcaneal facet is supported by the sustentaculum tali and articulates with the middle facet of the talus. The anterior calcaneal facet articulates with the anterior talar facet and is supported by the calcaneal beak. The triangular anterior surface of the calcaneus articulates with the cuboid ( Fig. 1 ).

The lateral surface is flat and subcutaneous, with a central peroneal tubercle for the attachment of the calcaneofibular ligament centrally. The lateral talocalcaneal ligament attaches anterosuperiorly to the peroneal tubercle. Medially, the talus is held to the calcaneus firmly by the interosseous ligament and the thick medial talocalcaneal ligaments.  The sustentaculum tali is seen at the anterior aspect of the medial surface. The groove inferior to it transmits the flexor halluces longus tendon . The neurovascular bundle runs adjacent to the medial border of the calcaneus ( Fig. 2 ). It may be injured during trauma or during surgery by the reduction of the sustentacular fragment, which is a key element in the surgical management of calcaneal fractures.

A high-energy trauma which causes axial loading is the most common cause of calcaneal fractures. Excessive axial force drives the lateral process of the talus into the angle of Gissane. As the posterior facet of the calcaneus rotates anteriorly, it transmits this force to the calcaneus. As resistance is exceeded, a primary fracture line is generated through the angle of Gissane and the neutral triangle. A secondary fracture line can be generated with greater forces and usually has two possible exits: the upper or the posterior calcaneal surface ( Fig. 3 ). Although this is the most commonly observed pattern, greater forces may generate additional or different fracture lines.

CT has revolutionized the assessment of calcaneal fractures by providing detailed information of the fracture pattern and thus guiding treatment.