Calcaneus Bone – Anatomy, Nerve Supply, Muscle Attacthment

Calcaneus Bone is a large and strong bone that forms the back of the foot and transfers most of the body weight from the lower extremity to the ground. It is the largest of the seven articulating bones that make up the tarsus. The calcaneus is located in the hindfoot with the talus and articulates with the talus and cuboid bones. Numerous ligaments and muscles attach to the calcaneus and help with its role in human bipedal biomechanics.[rx]

Anatomy of Calcaneus Bone

The calcaneus is a roughly rectangular prism-shaped bone located inferior to the talus and posterior to the midfoot. The long axis of the prism extends approximately along the mid-line of the foot. To understand the calcaneus structure, it is necessary to examine its six surfaces separately.

The posterior surface of the calcaneus has a circular convex structure with three distinct facets. The middle facet serves as the attachment site for the calcaneal tendon (Achilles tendon), while the superior facet is separated from the calcaneal tendon by the retrocalcaneal bursa. The inferior facet bends towards the lower calcaneal surface to form the calcaneal tuberosity, the lowest part of the posterior calcaneal surface. The lower calcaneal surface or plantar surface forms from the forward protrusion of the calcaneal tuberosity, which leads to the formation of medial and lateral processes on both sides, and the calcaneal tubercle in the front.

The lateral calcaneal surface is a wide, flat surface, except for the two bony protrusions on it. The protrusion in the front is the peroneal tubercle (fibular trochlea) above and below which the tendons of the fibularis brevis and fibularis longus muscles pass, respectively. The protrusion in the back is a small bony elevation that gives attachment to the calcaneofibular ligament. The medial calcaneal surface is home to a bone protrusion, called sustentaculum tali, which carries the middle talar articular facet (one of the three talocalcaneal joint facets). And in the inferior aspect of the sustentaculum tali, there exists a groove that houses the flexor hallucis longus tendon.

The superior calcaneal surface hosts the anterior and posterior talar articular facets. The groove between these two facets so-called the calcaneal sulcus, and the corresponding talar sulcus join together to form the tarsal sinus (sinus tarsi). The tarsal sinus is a quite large space located between the anterior portions of the calcaneus and talus, and it contains several neurovascular structures and ligaments, some portions of the subtalar joint capsule, and fat. The anterior calcaneal surface is the smallest face that has an articular facet for the calcaneocuboid joint.

The calcaneus articulates with talus through the talocalcaneal joint in which the contact between the two bones derives from the anterior, middle, and posterior facets. The talocalcaneal joint, also known as the subtalar joint, allows for essential foot motions such as inversion, eversion, dorsiflexion, and plantarflexion of the foot. Besides, the calcaneus serves as an attachment point for the Achilles tendon, which produces aids in plantar flexion of the foot vital for standing, walking, running, and jumping. The calcaneus serves as an attachment point also for muscles that move the toes. The bone has several joint stabilizing ligaments attached to it, such as the calcaneofibular, talocalcaneal, calcaneocuboid, and calcaneonavicular ligaments. The plantar aponeurosis and long plantar ligament support the arch of the foot and attach to the calcaneus as well.[rx][rx]

Blood Supply of Calcaneus Bone

The calcaneus is surrounded by and receives its blood supply from a superficial network of arteries called the calcaneal anastomosis, which is formed by branches of the posterior tibial and fibular arteries. Much of the lymphatic flow follows the vasculature and flows up the leg through the popliteal and inguinal lymph nodes before passing through the thoracic duct.[rx][rx]

Bony Landmarks of Calcaneus Bone

Nerves of Calcaneus Bone

The calcaneus receives its nerve supply from branches of the tibial and sural nerves. The calcaneal nerve branches include the medial calcaneal branches of the tibial nerve and lateral calcaneal branches of the sural nerve.[rx][rx]

Muscles Attachment of Calcaneus Bone

Three muscles join together to form the Achilles tendon and connect to the calcaneal tubercle. Additionally, six muscles originate from the calcaneal surface and disperse to the areas where they function.

• The gastrocnemius, soleus, and plantaris – They are the primary plantar flexors that combine to form the Achilles tendon. The Achilles tendon attaches to the calcaneal tubercle.
• The extensor digitorum brevis – It originates on the dorsolateral side of the calcaneus and provides an extension of the second to fourth digits.
• The abductor hallucis – It originates on the medial process of calcaneal tuberosity and abducts the first digit.
• The extensor hallucis brevis – It originates on the dorsal aspect of the calcaneus and extends the first digit.
• The abductor digiti minimi – It originates on the calcaneal tubercle and provides flexion and extension of the fifth toe.
• The flexor digitorum brevis – It originates on the calcaneal tubercle and helps provide flexion to the second to fourth digits.
• The quadratus plantae – It originates on the lateral and medial processes of the calcaneus and helps provide flexion at the distal interphalangeal joint.[rx][rx]

Function

Three muscles insert on the calcaneus: the gastrocnemius, soleus, and plantaris. These muscles are part of the posterior compartment of the leg and aid in walking, running and jumping. Their specific functions include plantar flexion of the foot, flexion of the knee, and steadying the leg on the ankle during standing. The calcaneus also serves as origin for several short muscles that run along the sole of the foot and control the toes.

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