Calcaneus
The calcaneus is the heel’s largest tarsal, bearing body weight and anchoring the Achilles tendon.
The calcaneus, commonly referred to as the heel bone, is the largest and most posterior of the tarsal bones. It forms the foundation of the rearfoot and serves as the primary weight-bearing bone of the foot during standing and locomotion. The calcaneus articulates with the talus superiorly to form the subtalar joint and with the cuboid anteriorly as part of the midfoot. Its robust structure, numerous articular facets, and ligamentous and muscular attachments make it a crucial element in foot mechanics and gait.
Structure
The calcaneus is an irregularly shaped bone with a complex anatomy that includes prominent bony processes, grooves, and articular surfaces. Internally, it consists of a cancellous trabecular network enclosed by dense cortical bone. Its external features are adapted to transmit forces from the leg to the ground while accommodating muscular leverage and tendon passage.
Surfaces and Features
- Superior surface: Articulates with the talus at three distinct facets — anterior, middle, and posterior — separated by the sulcus calcanei.
- Inferior surface: Rough and irregular, contains the weight-bearing heel region that contacts the ground during heel strike.
- Anterior surface: Articulates with the cuboid bone at the calcaneocuboid joint.
- Posterior surface: Features the calcaneal tuberosity and medial/lateral processes, serves as the attachment for the Achilles tendon.
- Medial surface: Presents the sustentaculum tali, a horizontal shelf that supports the talus and serves as a ligament and tendon passage area.
- Lateral surface: Marked by the peroneal (fibular) trochlea, a bony ridge guiding the tendons of the fibularis muscles.
Location
The calcaneus is located in the posterior part of the foot, forming the heel. It lies inferior to the talus and posterior to the cuboid. The bone projects posteriorly beyond the ankle joint and contacts the ground during standing and ambulation.
- Superior: Talus (via subtalar joint)
- Anterior: Cuboid (via calcaneocuboid joint)
- Posterior: Skin and subcutaneous tissue of the heel pad
- Medial: Sustentaculum tali adjacent to the tarsal tunnel
- Lateral: Peroneal tendons pass along this side
Function
- Weight-bearing: Transmits body weight from the talus to the ground during heel strike and stance phase of gait
- Shock absorption: Cushions impact forces through its trabecular bone and overlying soft tissue
- Joint articulation: Facilitates inversion and eversion of the foot via subtalar joint movement
- Leverage: Provides a mechanical advantage for the triceps surae muscles during plantarflexion
Articulations
The calcaneus articulates with two bones:
Bone | Joint | Type |
---|---|---|
Talus | Subtalar joint | Synovial plane |
Cuboid | Calcaneocuboid joint | Synovial saddle (modified) |
Articular Facets
- Posterior facet: The largest; concave surface for articulation with the talus
- Middle facet: Located on the sustentaculum tali
- Anterior facet: Flat or convex, articulates with the anterior talus
The sulcus calcanei lies between the middle and posterior facets and combines with the talar sulcus to form the sinus tarsi, a channel for ligaments and neurovascular structures.
Ligament Attachments
The calcaneus anchors multiple ligaments that support the hindfoot and maintain arch integrity:
Ligament | Attachment Site | Function |
---|---|---|
Plantar calcaneonavicular (spring) ligament | Sustentaculum tali to navicular | Supports head of talus and medial arch |
Long plantar ligament | Calcaneal tuberosity to bases of metatarsals | Stabilizes lateral arch |
Short plantar (calcaneocuboid) ligament | Anterior calcaneus to cuboid | Supports calcaneocuboid joint |
Interosseous talocalcaneal ligament | In sinus tarsi between talus and calcaneus | Stabilizes subtalar joint |
Muscle Attachments
The calcaneus serves as an origin or insertion point for several muscles:
Muscle | Attachment | Function |
---|---|---|
Gastrocnemius | Via Achilles tendon to calcaneal tuberosity | Plantarflexion of foot |
Soleus | Via Achilles tendon to calcaneal tuberosity | Plantarflexion |
Plantaris | Variable insertion near medial tuberosity | Assists plantarflexion |
Abductor hallucis | Medial process of calcaneal tuberosity | Abducts great toe |
Abductor digiti minimi | Lateral process of tuberosity | Abducts little toe |
Flexor digitorum brevis | Central calcaneal tuberosity | Flexes lateral four toes |
Quadratus plantae | Medial and lateral calcaneus | Assists flexor digitorum longus |
Blood Supply
The calcaneus is supplied by branches of the posterior tibial artery, peroneal (fibular) artery, and lateral plantar artery. These vessels form an extensive network around the bone, particularly near the tuberosity and sustentaculum tali.
- Posterior tibial artery: Primary supply to medial aspect
- Peroneal artery: Supplies lateral and posterior regions
- Lateral plantar artery: Supplies plantar surface
Nerve Supply
The calcaneus is innervated by sensory and motor branches of the:
- Medial calcaneal branches (tibial nerve): Innervate medial and plantar heel skin
- Lateral plantar nerve: Supplies muscles arising from lateral tuberosity
- Sural nerve: Provides cutaneous innervation to lateral heel
Ossification
The calcaneus ossifies from a primary center that appears during fetal development, along with a secondary center in the posterior tuberosity.
- Primary center appears: 5th–6th fetal month
- Secondary ossification center (calcaneal apophysis): Appears around age 6–8, fuses by age 14–16
Clinical Significance
- Calcaneal fractures: Commonly occur from high-energy axial loading (e.g., falls). Intra-articular types affect the subtalar joint and may require ORIF (open reduction internal fixation).
- Calcaneal apophysitis (Sever’s disease): Common in athletic children; due to repetitive stress on the secondary ossification center.
- Heel spur syndrome: Bony projection from the tuberosity associated with chronic plantar fasciitis; visible on lateral foot X-ray.
- Bursitis: Retrocalcaneal and subcutaneous bursae over the tuberosity may become inflamed from friction or overuse.
- Tarsal coalition: Congenital fusion between the calcaneus and talus or navicular limits motion and causes chronic pain or flatfoot deformity.
Imaging
- X-ray: Standard lateral, axial (Harris-Beath), and oblique views assess fracture patterns and alignment
- CT scan: Crucial for evaluating intra-articular fractures and sinus tarsi detail
- MRI: Used for soft tissue injuries, marrow edema, and chronic heel pain assessment
- Ultrasound: Helps visualize Achilles tendon insertion and retrocalcaneal bursae
Last updated on May 21, 2025