10 (2005) 413–424

The Anatomy of the Calcaneus and

Surrounding Structures

Brian J. Keener, MD, Joseph A. Sizensky, MD*

Department of Orthopaedics and Rehabilitation, Pennsylvania State University,

Milton S. Hershey Medical Center, 500 University Drive, MSHMC-UPC,

Hershey, PA 17033-0850, USA

Appreciation of the normal anatomy of the calcaneus is significant for various

reasons. Restoration of normal anatomy has been of particular interest for fracture

care. In addition, knowledge of surrounding structures is important when plan-

ning surgical approaches and vital when performing percutaneous procedures.

Understanding of anatomic relationships allows discernment of the pathophysi-

ology that is related to chronic conditions. The biomechanics of normal structures

provides a theoretic basis for reconstruction and rehabilitation, and individual

variations in calcaneal anatomy can be a predisposition for pathology.

Topographic anatomy

The medial aspect of the calcaneus is difficult to palpate because of the

intervening soft tissue structures. The posterosuperior calcaneal tuberosity

typically can be distinguished as well as the sustentaculum, which lies approxi-

mately one finger breadth below the tip of the medial malleolus. The plantar

surface of the calcaneus is obscured largely by the heel pad; however, the larger

and broader medial process of the calcaneal tuberosity frequently is palpable

compared with the small lateral process. Dorsiflexion of the toes can bring the

plantar fascia into tension and allow palpation of its insertion into the distal

aspect of the medial tuberosity. The proximal plantar skin covers the rounded

posterior inferior border of the calcaneus. Posteriorly, the skin thins and allows

Foot Ankle Clin N Am

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doi:10.1016/j.fcl.2005.04.003 foot.theclinics.com

* Corresponding author.

E-mail address: jsizensky@psu.edu (J.A. Sizensky).

keener & sizensky414

palpation of the Achilles tendon as it inserts into the posterior surface of the

calcaneus. The medial and lateral borders are well-defined here.

From the prominent superolateral corner of the tuberosity moving inferiorly,

the lateral tubercle can be palpated through the glabrous skin. The abductor digiti

minimi defines the posteroinferior lateral border of the foot. Dorsal to the lateral

malleolus, the peroneal tubercle can be palpated. The sinus tarsi can be identified

by noticing the soft tissue depression just anterior to the lateral malleolus. Further

distal and more inferior, approximately two thirds the distance from the lateral

malleolus to the base of the easily palpated fifth metatarsal, is the calcaneocuboid

joint. The anterior process of the calcaneus can be identified here if the forefoot

is adducted.

Bone morphology

The calcaneus is the largest of the seven tarsal bones, transmits body weight,

and provides a strong lever. There are four articular surfaces to the calcaneus

(Fig. 1). The superior surface of the calcaneus is divided into an anterior portion

that contains three articular facets for articulation with the talus, and a posterior

portion that is smooth and terminates as the calcaneal tuberosity. The posterior

facet is the largest of these, and is oval and convex along its longitudinal axis,

which runs distal and lateral 458 to the sagittal plane. Because only the central

portion of the facet is visible on axial (Harris-Beath) views, Broden’s views that

are taken with the beam directed at multiple angles allow evaluation of the entire

facet [1]. The sulcus calcaneus, which separates the middle facet from the

posterior facet, is the floor of the tarsal canal. The tarsal canal empties laterally

and distally into the sinus tarsi, and within it are five ligaments—the three

portions of the inferior extensor retinaculum, the oblique talocalcaneal (cervical)

ligament, and the ligament of the tarsal canal [2]. The middle facet, located on

the upper surface of the sustentaculum tali, is concave and oval. The anterior

facet is anterolateral to the middle facet and supported by the beak of the cal-

Fig. 1. The calcaneal facets are pictured from a superior view. A, anterior facet; C, calcanealcuboid

facet; M, middle facet; P, posterior facet.

anatomy of the calcaneus 415

caneus. The middle and anterior facets have a variable anatomy [3]. Viladot and

colleagues [3] described three variations: a combined facet, two separate facets,

or congruent facets in a bean shape. The anterior and middle facets, the posterior

articular surface of the navicular, and the plantar calcaneonavicular (spring)

ligaments combine to form the acetabulum pedis, which contains the head of the

talus [4]. The cuboid articular surface makes up the entire anterior surface of the

calcaneus. It is convex horizontally and concave vertically which results in a

saddle shape [5].

The bulk of the calcaneus is composed of cancellous bones contained by a

thin cortical shell. Laterally, the anterior process aids in supporting the lateral

process of the talus. Posterior and lateral to the anterior process is the eminentia

trochlearis, or peroneal tubercle, which is the site of insertion for the peroneal

retinaculum (Fig. 2). The peroneal trochlea is just posterior to this and separates

the peroneal tendons. The superior groove transmits the peroneus brevis tendon,

whereas the inferior groove transmits the peroneus longus tendon. Postero-

inferiorly, there are two tuberosities that transmit the force of the body weight

(Fig. 3) [6]. The medial tuberosity is the larger of the two. The medial surface of

the calcaneus is dominated by the sustentaculum tali (Fig. 4). The inferior surface

of the sustentaculum tali is grooved for the flexor hallucis longus tendon. The

talocalcaneal component of the deltoid ligament and the superomedial

calcaneonavicular ligament also attach to this area of strong cortical bone. On

a Harris-Beath axial radiograph, sustentaculum tali is identified as the prominent

medial projection and on the lateral radiograph, it is distinct secondary to its

being denser than the surrounding bone. The sustentaculum also forms the lateral

boundary of the tarsal tunnel with the talus.

A triangle is formed by the trabeculae of the calcaneus when viewed laterally.

The apex of the triangle has been termed the thalamic portion of the calcaneus

and is where the pressure trabeculae converge to support the anterior and

posterior facets. The base of the triangle is made up of the traction trabeculae that

Fig. 2. Lateral view of the calcaneus. B, Bohler’s angle; G, crucial angle of Gissane; P,

peroneal tubercle.

Fig. 3. Posterior view of the calcaneus. L, lateral process of calcaneal tuberosity; M, medial process of

calcaneal tuberosity; S, sustentaculum tali.

keener & sizensky416

radiate from the inferior cortex. The blood supply to the medullary cavity is

believed to enter at the center of the triangle [7,8]. The crucial angle of Gissane

also can be viewed on the lateral radiograph. Typically 1208 to 1458, it is formed

by a line from the anterior process to the sulcus calcaneus and a line along the

posterior facet. The lateral process of the talus sits within the strong cortical struts

that make up the angle of Gissane, and typically is the site of the primary fracture

line in joint depression-type calcaneal fractures [5,9–11]. Bohler’s angle is

formed by a line from the highest point on the calcaneal tuberosity to the highest

point on the posterior articular surface and a line that extends from the highest

point on the anterior process through the highest point on the posterior articular

surface. Normal angles typically are reported as being between 258 and 408 and a

decrease in this angle helps to quantify the degree of compression and deformity

in joint depression fractures (see Fig. 2) [9,12,13].

Fig. 4. Medial view of the calcaneus. S, sustentaculum tali; T, calcaneal tuberosity.

anatomy of the calcaneus 417

Nerves and vessels

The cutaneous blood supply to the skin surrounding the calcaneus is from the

peroneal and posterior tibial arteries and its two branches, the medial and lateral

plantar arteries. The lateral incision to the calcaneus is at risk for necrosis because

of its location in the watershed between the peroneal, posterior tibial, and lateral

plantar arteries [14]. The calcaneus itself is more vascular. Andermahr and

colleagues [15] found that 10% of the blood supply is from the sinus tarsi artery,

and the remainder is divided equally between the lateral and plantar arteries. The

medial supply is from two or three arteries, generally branches of the posterior

tibial artery or lateral plantar artery that penetrate the bone inferior to the

sustentaculum. The lateral supply typically is from the lateral calcaneal artery off

the posterior tibial artery, but occasionally is from the peroneal artery. The sinus

tarsi artery is formed from branches of the lateral tarsal and lateral malleolar

branches of the anterior tibial artery [2].

Laterally, the cutaneous innervation is from the lateral sural cutaneous nerve

and the sural nerve and its lateral calcaneal branch. Innervation is provided by the

saphenous nerve posteromedially, the superficial peroneal nerve anteriorly, and

the medial calcaneal branch of the tibial nerve inferomedially [16].

The calcaneocuboid joint receives innervation from the lateral plantar, deep

peroneal, and lateral dorsal cutaneous nerves. The talonavicular joint receives

innervation from the medial plantar and deep peroneal nerves. The subtalar joint

is innervated by the medial plantar and lateral dorsal cutaneous nerves. Occa-

sionally, the superficial peroneal nerve continues into the accessory deep peroneal

nerve and provides additional branches to the subtalar and calcaneocuboid

joints [17].

Joints and ligaments

The calcaneus has three articulations: subtalar, talocalcaneonavicular, and

calcaneocuboid (Fig. 5). Anatomically, the subtalar joint is composed of the

posterior facet of the calcaneus and the posterior articular surface of the talar

body. Clinically, the subtalar joint also includes an anterior articulation, al-

though they have two separate capsules. The posterior articulation is separated

from the subtalar portion of the talocalcaneonavicular joint by the inferior

extensor retinaculum and by the talocalcaneal interosseous ligament (Fig. 6).

Cahill [18] described two parts of the inferior extensor retinaculum: the cru-

ciate ligament in the tarsal canal and the oblique talocalcaneal band. Smith [19]

identified two parts to the talocalcaneal interosseous ligament: the ligament of

the tarsal canal and the cervical ligament. Additional support medially comes

from the tibiocalcaneal portion of the deltoid ligament and the medial talo-

calcaneal ligament that is located posteriorly to it. Laterally, there is the cal-

caneofibular ligament and anterior to it is the lateral talocalcaneal ligament

(Fig. 7) [16].

Fig. 5. Three views of the calcaneus. (A) Lateral view. (B) Medial view. (C) Posterior view. L, lateral

process of calcaneal tuberosity; M, medial process of calcaneal tuberosity; S, sustentaculum tali.

keener & sizensky418

The talocalcaneonavicular joint is one continuous joint cavity and functions

with the subtalar joint. The talonavicular section is part of the transverse tarsal

joint and the dorsolateral portion of the capsule is made up of the calcaneona-

vicular portion of the bifurcate ligament. The bifurcate ligament is composed of a

calcaneonavicular limb that extends from the anteromedial angle of the sinus tarsi

Fig. 6. Inferior view of talus and superior view of calcaneus illustrating the subtalar joint and its facets.

A, anterior facet of the calcaneus; M, middle facet of the calcaneus; P, posterior facet of the calcaneus;

T, posterior facet of the talus.

Fig. 7. (A) Inferior medial view of the calcaneus and surrounding structures. (B) Lateral view of

calcaneus and bifurcate ligament composed of the calcaneonavicular (Cn) and calcaneocuboid (Cc)

ligaments. F, calcaneal tuberosity; H, talar head; L, plantar calcaneonavicular (spring) ligament.

anatomy of the calcaneus 419

to the lateral aspect of the navicular, and a calcaneocuboid limb that extends from

the intermediary tubercle of the calcaneus to the dorsal aspect of the cuboid and

arranged in a ‘‘Y’’ or ‘‘V’’ configuration (Fig. 8) [20]. As in most of the foot, the

plantar ligaments are the strongest and most important. The plantar calcaneona-

vicular ligament (spring ligament) complex is composed of a quadrangular

superomedial band (the superomedial calcaneonavicular ligament) which runs

from the anterior and medial margins of the sustentaculum tali to the medial one

third of the navicular, a trapezoidal inferior band (the inferior calcaneonavicular

ligament) which runs from the coronoid fossa of the calcaneus below the anterior

and medial facets to the plantar aspect of the navicular in addition to the tibio-

ligamentous portion of the superficial deltoid ligament (see Fig. 8) [21,22]. It

helps to support the head of talus, and when disrupted, allows the talus to inter-

pose between the calcaneus and navicular which flattens the arch and abducts the

foot [16].

The calcaneocuboid joint is at the high point of the lateral longitudinal arch.

Dorsally, it is supported by the bifurcate ligament and plantarly it is supported by

the short and long plantar ligaments. The short plantar (plantar calcaneocuboid)

ligament is deep to the long plantar ligament and separated by loose connective

tissue. It runs from the anteroinferior surface of the calcaneus to the tuberosity of

the cuboid. The long plantar ligament is the main support for the lateral part of

the arch. Its calcaneal attachment is the entire inferior surface of the calcaneus

distal to the tuberosities. The deep fibers attach to the posterior aspect of the

groove for the peroneus longus tendon on the tuberosity of the cuboid. The su-

perficial fibers envelop the tendon and insert on the lateral metatarsal bases [16].

Muscles and tendons

The calcaneus serves as the origin and insertion of several muscles; additional

muscles also have a close anatomic relationship (Figs. 9 and 10). Plantarly, the

Fig. 8. Ligaments of the ankle joint. The medial view shows the medial ligament, which forms a

dense, almost continuous ligament. The ligaments on the lateral side, however, are usually separated

from one another. From Gardner ED, Muller F, et al. Gardner-Gray-O’Rahilly anatomy: a regional

study of human structure. Philadelphia: Saunders; 1986.

keener & sizensky420

most superficial layer is the plantar aponeurosis; it runs from the medial

tuberosity distally to the middle of the foot where it sends slips to each of the five

digits. The most superficial muscle layer consists of the abductor hallucis and

flexor digitorum brevis—both arise from the medial tuberosity—and the abductor

digiti minimi that arises from the lateral tuberosity and plantar surface of the

calcaneus. There also are some fibers from the medial tuberosity deep to the

flexor digitorum brevis. All of these muscles insert onto the proximal phalanges

and help to maintain the longitudinal arch. The medial and lateral plantar nerves

pass deep to the abductor hallucis. The medial plantar nerve comes medial to the

flexor digitorum brevis muscle and sends motor branches to the abductor

hallucis, flexor digitorum brevis, and the first lumbrical. The lateral plantar nerve

courses between the flexor digitorum brevis and the quadratus and innervates the

abductor digiti minimi; quadratus plantae; the lateral three lumbricals; the second,

third, and fourth interossei; and the transverse head of the adductor hallucis [16].

The deeper layer is made up of the quadratus plantae and tendons of the flexor

hallucis longus and flexor digitorum longus. The tendon of the flexor digitorum

Fig. 9. The right calcaneus, upper aspect, showing muscular and ligamentous attachments in the floor

of the sinus tarsi and tarsal canal. From Gardner ED, Muller F, et al. Gardner-Gray-O’Rahilly

anatomy: a regional study of human structure. Philadelphia: Saunders; 1986.

anatomy of the calcaneus 421

longus passes superficial to the quadratus plantae and flexor hallucis longus

tendon and deep to the medial plantar nerve in its course to the lesser toes. The

quadratus plantae takes its insertion from the calcaneus in two heads that are

located medial and lateral to the long plantar ligament. The lateral head—the

more tendinous of the two—is variable and occasionally is missing or takes its

origin from the fibula [23]. It joins with the medial head to insert on the deep

surface of the flexor digitorum longus, typically at the level of its division into

Fig. 10. Schematic section (approximately coronal) or right calcaneus and talus. This is a composite

representation, not all of the structures being present in any one section. From Gardner ED,

Muller F, et al. Gardner-Gray-O’Rahilly anatomy: a regional study of human structure. Philadelphia:

Saunders; 1986.

keener & sizensky422

four separate tendons. It is innervated by the lateral plantar nerve that runs

superficial to it [16].

Dorsally, the calcaneus gives rise to the extensor brevis muscles. It is unique

in that there is no counterpart to the hand, and although it inserts on four toes,

they are the medial four rather than the lateral four. Generally, the most medial

belly is defined as the extensor hallucis brevis, and the lateral three make up the

extensor digitorum brevis. They arise from the superior surface of the calcaneus

just proximal to the calcaneocuboid joint. Their deep surface receives the termi-

nal muscular branch from the deep peroneal nerve, and occasionally, they receive

a contribution from the superficial peroneal nerve [16].

Posteriorly, the calcaneus serves as the insertion of the Achilles and plantaris

tendons. The tendo Achilles comprises the tendons of the soleus and gastro-

cnemius. The soleus muscle is anterior to the gastrocnemius; however, as it

descends to insert into the calcaneus, it rotates approximately 908 so that the

soleus fibers insert mostly medially and the gastrocnemius fibers insert mostly

laterally [24,25]. The insertion is on the inferior posterior surface, more medial

than lateral, but does not extend to either wall [26]. Superior to its insertion is the

retrocalcaneal bursa between the posterior calcaneus and the tendon (Fig. 11).

A continuous heavy layer of collagen fibers continues from the Achilles tendon

into the plantar fascia in neonates [27]. With age, these fibers decrease in number

such that by late adulthood, these fibers seem to be absent. The plantaris inserts

just medial to the tendo Achilles.

Medially, the posterior tibial tendon, flexor digitorum longus tendon, posterior

tibial artery and vein, tibial nerve, and flexor hallucis longus tendon pass deep to

the flexor retinaculum and superficial to the deltoid ligament on their course into

the foot. Their location is important to consider, especially when inserting

percutaneous anteromedial transcalcaneal pins. Mekhail and colleagues [28]

found that when placing a pin into the sustentaculum tali 2.5 cm distal to the

medial malleolus, the neurovascular bundle is 1 cm posteroinferior. In their

cadaver study, the flexor tendons were transfixed 4 out of 14 times. They found a

Fig. 11. The retrocalcaneal bursa lies between the retracted Achilles tendon (T) and the calcaneal

tuberosity (C).

Fig. 12. Superficial lateral view of calcaneus illustrating relationship to the peroneal tendons. The

instrument tip is on the peroneal tubercle.

anatomy of the calcaneus 423

safer alternative to be the posteromedial transcalcaneal pin site, which is located

three fourths of the distance between the medial malleolus and the medial

calcaneal tubercle; although the medial calcaneal artery and nerve are still at risk,

injury may be avoided with blunt dissection [28].

Laterally, the peroneus longus tendon passes posteroinferior to the peroneus

brevis tendon, which runs in a groove in the posterior fibula under the superior

and inferior peroneal retinaculum (Fig. 12). The inferior peroneal retinaculum

divides the two tendons into separate sheaths. The calcaneus contains a groove

for the peroneus longus, and occasionally, is an insertion for an accessory

peroneal muscle [29].

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