1.4 Bones of Foot

Introduction

• The foot is a specialized structure designed for weight bearing and locomotion.
• The bones of the foot provide a strong framework that supports the soft tissues and enables efficient movement.
• Each foot contains 26 bones, arranged as follows:
  • Tarsal bones: 7
  • Metatarsal bones: 5
  • Phalanges: 14
  • Total: 26 bones
• The foot has two surfaces:
  • The dorsum (upper surface).
  • The sole (plantar or lower surface), which comes into contact with the ground during standing and walking.
• Each foot has five toes, arranged from medial to lateral:
  • Great toe (hallux)
  • Second toe
  • Third toe
  • Fourth toe
  • Little (fifth) toe
• Each toe consists of three phalanges, except the great toe, which contains two phalanges.

Tarsal Bones

• The tarsus consists of seven tarsal bones, which form the posterior part of the foot.
• The seven tarsal bones are:
  1. Talus
  2. Calcaneus
  3. Navicular
  4. Medial cuneiform
  5. Intermediate cuneiform
  6. Lateral cuneiform
  7. Cuboid

• The tarsal bones are arranged in three rows:

• Proximal row:
  • Talus (superiorly placed)
  • Calcaneus (inferiorly placed)
• Middle row:
  • Navicular
• Distal row (from medial to lateral):
  • Medial cuneiform
  • Intermediate cuneiform
  • Lateral cuneiform
  • Cuboid

• Mnemonic: Teacher Called Naresh, Meet In Lecture Class

Talus

• The talus is the primary bone that connects the leg to the foot.
• It forms the central component of the ankle (talocrural) joint.
• The talus is unique among the tarsal bones because it has no muscular attachments.

Parts of talus

The talus consists of three parts:

• Head: Rounded and directed forward.
• Neck: Narrow constricted region behind the head.
• Body: Expanded posterior part with a convex superior facet, triangular lateral facet, and comma-shaped medial facet.

Side determination and anatomical position

• Keep the head directed forward, downward, and medially.
• Ensure the convex superior articular surface faces upward.
• The large triangular lateral facet should face the side to which the bone belongs.

Features of talus

• The talus consists of three parts: head, neck, and body.
• It is the keystone of the ankle joint and participates in multiple articulations with the tibia, fibula, calcaneus, and navicular.

Head of talus

• The head is directed forward, downward, and medially.
• Its anterior convex articular surface articulates with the navicular to form the talonavicular joint. (Identification feature)
• The inferior surface bears three articular facets:
  1. Anterolateral facet: Articulates with the anterior facet of the calcaneus.
  2. Middle facet: Articulates with the sustentaculum tali.
  3. Posterior facet: Articulates with the middle facet of the calcaneus.

Neck of talus

• The neck is the constricted region connecting the head and body.
• Its long axis forms an angle of approximately 150° with the body.
• The superior surface is rough and provides attachment to the dorsal talonavicular ligament.
• The inferior surface contains the sulcus tali, which joins the calcaneal groove to form the sinus tarsi.
• The interosseous talocalcaneal ligament attaches within the sulcus tali.

Body of talus

• The body is cuboidal and has five surfaces: superior, inferior, medial, lateral, and posterior.
• The superior (trochlear) surface is convex anteroposteriorly, slightly concave transversely, and wider anteriorly. It articulates with the distal tibia and provides attachment to the ankle joint capsule.
• The medial surface has a comma-shaped articular facet for the medial malleolus.
• The lateral surface has a large triangular articular facet for the lateral malleolus.
• The inferior surface bears a deep concave facet that articulates with the calcaneus and provides attachment to the interosseous and cervical talocalcaneal ligaments.
• The posterior surface contains a groove for the tendon of flexor hallucis longus (FHL).
• The margins of this groove form the medial and lateral tubercles.
• In about 5% of individuals, the lateral tubercle remains separate as the os trigonum, an important anatomical variant.
• The medial tubercle gives attachment to the superficial fibers of the deltoid ligament and the medial talocalcaneal ligament.

Ossification

The talus ossifies from a single primary ossification center, which appears during the 6th month of intrauterine life.

Calcaneus (Calcaneum)

• Calcaneus (calcaneum) is the largest and strongest tarsal bone and forms the bony prominence of the heel.
• It is an irregular cuboidal bone, with its long axis directed forward, upward, and laterally.

Part of calcaneus

• The calcaneus has six surfaces: anterior, posterior, superior, inferior, medial, and lateral.
  1. The anterior surface bears a concavo-convex articular facet for articulation with the cuboid.
  2. The posterior surface is rough and non-articular, providing attachment for soft tissues.
  3. The superior surface contains a large oval articular facet for the talus.
  4. The inferior surface forms the calcaneal tuberosity, which transmits body weight to the ground.
  5. The lateral surface is rough and flat.
  6. The medial surface presents the sustentaculum tali, a shelf-like projection that supports the talus.

Anatomical position and side determination

• For side determination, the anterior articular facet faces forward, upward, and laterally, the superior oval facet faces upward, and the sustentaculum tali projects medially, indicating the side of the bone.

Features of calcaneus

• The calcaneus has six surfaces: Anterior, posterior, superior, inferior, medial, and lateral.

Anterior surface

• The anterior surface is the smallest surface of the calcaneus.
• It bears a triangular concavo-convex articular facet.
• It articulates with the cuboid bone, forming the calcaneocuboid joint.

Posterior surface

• The posterior surface is rough and non-articular and is divided into upper, middle, and lower areas.
• The upper area is related to the retrocalcaneal synovial bursa.
• The middle area receives the insertion of the calcaneal (Achilles) tendon formed by the gastrocnemius and soleus muscles.
• The plantaris tendon inserts along the medial margin of the middle area.
• The lower area provides attachment for fibrofatty tissue and helps support body weight during standing.

Superior (dorsal) surface

• The superior surface is divided into anterior, intermediate, and posterior areas.
• The posterior area is rough and non-articular.
• The intermediate area bears the posterior articular facet for the talus.
• The anterior area contains the anterior and middle articular facets for the talus.
• A sulcus calcanei lies medially and provides attachment for the interosseous talocalcaneal and cervical ligaments.
• The lateral part gives origin to the extensor digitorum brevis and attachment to the inferior extensor retinaculum and bifurcate ligament.

Inferior (plantar) surface

• The inferior surface is rough and irregular and contains anterior, medial, and lateral tubercles.
• The medial and lateral tubercles form the calcaneal tuberosity, with the medial tubercle being larger.
• The medial tubercle gives origin to the abductor hallucis and flexor digitorum brevis and provides attachment for the flexor retinaculum and plantar aponeurosis.
• The lateral tubercle gives origin to the abductor digiti minimi.
• The anterior tubercle provides attachment for the short plantar ligament.
• The area between the tubercles gives attachment to the long plantar ligament.

Medial surface

• The medial surface projects as the sustentaculum tali, a shelf-like process that supports the talus.
• The inferior surface of the sustentaculum tali contains a groove for the tendon of flexor hallucis longus.
• The groove gives attachment to the deep part of the flexor retinaculum.
• The medial surface provides attachment, from anterior to posterior, to the spring ligament, tibialis posterior tendon, deltoid ligament, and medial talocalcaneal ligament.

Lateral surface

• The lateral surface is rough and flat.
• It bears the peroneal (fibular) trochlea, which serves as a pulley for the fibular tendons.
• The inferior peroneal retinaculum attaches to the peroneal trochlea.
• The peroneus brevis tendon passes above the trochlea, while the peroneus longus tendon passes below it.

Ossification of calcaneus

• The calcaneus develops from one primary and one secondary ossification center.
• The primary ossification center appears during the 3rd month of intrauterine life.
• The secondary ossification center appears between 6 and 8 years of age.
• The secondary center fuses with the primary center between 14 and 16 years.

Navicular Bone

• The navicular is a boat-shaped tarsal bone located on the medial side of the foot, between the talus and the three cuneiform bones.

Features of navicular

• It has six surfaces: anterior, posterior, superior, inferior, medial, and lateral.
  1. The anterior surface is convex and bears three articular facets for the cuneiform bones.
  2. The posterior surface has a concave oval facet that articulates with the head of the talus.
  3. The superior (dorsal) surface is rough, convex, and non-articular, providing attachment for the talonavicular, dorsal cuneonavicular, and cubonavicular ligaments.
  4. The inferior (plantar) surface has a groove for the tendon of tibialis posterior and a bony projection that provides attachment for the spring ligament.
  5. The medial surface bears the navicular tuberosity, which receives the major insertion of the tibialis posterior tendon.
  6. The lateral surface is rough and is mostly non-articular.

Side determination and anatomical position

• The anterior surface with three articular facets faces forward, while the concave posterior surface faces backward.
• The grooved inferior surface is directed downward.
• The navicular tuberosity projects medially, indicating the side of the bone.

Ossification of navicular bone

The navicular ossifies from a single secondary ossification center, which appears at approximately 3 years of age.

Cuneiform Bones

• The cuneiform bones are three wedge-shaped tarsal bones located in the distal row of the tarsus.
• They are named medial, intermediate, and lateral cuneiforms.
• Each bone has a broad base and a narrow edge, giving it a characteristic wedge shape.
• The medial cuneiform is the largest, whereas the intermediate cuneiform is the smallest of the three.
• These bones articulate proximally with the navicular and distally with the first three metatarsals, contributing to the stability and arches of the foot.

Medial cuneiform

• The medial cuneiform is the largest of the three cuneiform bones.
• It has six surfaces: superior, inferior, anterior, posterior, medial, and lateral.

Features

• The superior (dorsal) surface forms a narrow, rough edge.
• The inferior (plantar) surface is broad and receives the insertion of the tibialis posterior tendon.
• The anterior surface bears a kidney-shaped articular facet for the base of the first metatarsal.
• The posterior surface has a triangular articular facet for the navicular bone.
• The lateral surface contains an inverted L-shaped articular facet for the intermediate cuneiform and second metatarsal. Its anteroinferior part receives the insertion of the peroneus (fibularis) longus tendon.
• The medial surface is rough and subcutaneous. The tibialis anterior tendon inserts at its anteroinferior angle.

Side determination and anatomical position

• The narrow edge is directed upward, and the broad base faces downward.
• The anterior surface with the kidney-shaped facet faces forward.
• The inverted L-shaped facet on the lateral surface indicates the side to which the bone belongs.

Ossification medial cuneiform

• The medial cuneiform ossifies from a single secondary ossification center, which appears during the 2nd year of life.

Intermediate cuneiform

• The intermediate cuneiform is the smallest of the three cuneiform bones.
• It has six surfaces: superior, inferior, anterior, posterior, medial, and lateral.

Features

• The superior (dorsal) surface is broad and forms the base of the wedge.
• The inferior (plantar) surface is narrow and forms the edge of the wedge. It receives a slip of the tibialis posterior tendon.
• The medial surface bears an inverted L-shaped articular facet for the medial cuneiform.
• The lateral surface has a vertical articular facet along its posterior margin for the lateral cuneiform.
• The anterior surface contains a triangular articular facet for the base of the second metatarsal.
• The posterior surface bears a triangular articular facet for the navicular bone.

 

Side determination and anatomical position

• The broad base is directed upward, while the narrow inferior edge faces downward.
• The vertical limb of the inverted L-shaped facet is directed posteriorly.
• The inverted L-shaped facet faces the opposite side to which the bone belongs.

Ossification of intermediate cuneiform

• The intermediate cuneiform ossifies from a single secondary ossification center, which appears during the 3rd year of life.

Lateral cuneiform

• The lateral cuneiform is a wedge-shaped tarsal bone with six surfaces: superior, inferior, anterior, posterior, medial, and lateral.

Features

• The superior (dorsal) surface is broad and forms the base of the wedge.
• The inferior (plantar) surface is narrow and forms the edge of the wedge. It receives a slip of the tibialis posterior tendon and gives origin to the flexor hallucis brevis.
• The anterior surface bears a triangular articular facet for the base of the third metatarsal.
• The posterior surface has a square-shaped articular facet for the navicular bone.
• The medial surface bears a vertical articular facet for the intermediate cuneiform and small anterior facets for the base of the second metatarsal.
• The lateral surface contains an oval articular facet for the cuboid and an inferior facet for the base of the fourth metatarsal.

Anatomical Position and Side Determination

• The broad superior surface faces upward, and the narrow inferior surface faces downward.
• The large triangular facet on the anterior surface is directed forward.
• The oval facet at the posterosuperior part of the lateral surface indicates the side of the bone.

Ossification

• The lateral cuneiform develops from a single ossification center, which appears during the 1st year of life.

Cuboid Bone

• The cuboid is the lateral-most bone of the distal row of the tarsus.
• It is situated between the calcaneus proximally and the fourth and fifth metatarsals distally.
• The cuboid has six surfaces: superior, inferior, anterior, posterior, medial, and lateral.

Features

• The superior (dorsal) surface is rough and flat and provides attachment for the dorsal calcaneocuboid, cubonavicular, and cubometatarsal ligaments.
• The inferior (plantar) surface contains an oblique groove for the peroneus (fibularis) longus tendon. A ridge behind the groove provides attachment for the long and short plantar ligaments. It also receives a slip of the tibialis posterior tendon and gives origin to fibers of the flexor hallucis brevis.
• The anterior surface bears a quadrangular facet for the fourth metatarsal and a triangular facet for the fifth metatarsal.
• The posterior surface has a large triangular articular facet for the calcaneus.
• The lateral surface is short and notched, allowing passage of the peroneus longus tendon.
• The medial surface bears anterior and posterior articular facets for the lateral cuneiform and navicular, respectively. It also provides attachment for the lateral limb of the bifurcate ligament.

Anatomical Position and Side Determination

• The grooved inferior surface faces downward.
• The anterior surface with the metatarsal facets faces forward.
• The notch on the lateral surface indicates the side to which the bone belongs.

Ossification

• The cuboid ossifies from a single primary ossification center, which appears just before birth.

Metatarsal Bones

• The metatarsals are five miniature long bones, numbered 1st to 5th from medial to lateral.
• Each metatarsal develops from one primary and one secondary ossification center.

General Features of Metatarsals

• Every metatarsal consists of three parts: base, shaft, and head.
• The base is the expanded posterior end.
• The shaft tapers from the base to the head, with a convex dorsal surface and a concave plantar surface.
• The head is rounded and articulates with the base of the proximal phalanx.

First Metatarsal Bone

• The first metatarsal is the shortest, thickest, and strongest and plays a major role in weight transmission.
• Its base has a kidney-shaped articular facet.
• The tibialis anterior and peroneus (fibularis) longus insert on the base.
• The first dorsal interosseous originates from the lateral surface of the shaft.

Second Metatarsal Bone

• The second metatarsal is the longest.
• Its wedge-shaped base bears a triangular posterior facet.
• The base articulates medially with the medial cuneiform and laterally with the lateral cuneiform and third metatarsal.
• The first and second dorsal interossei originate from its shaft.

Third Metatarsal Bone

• The third metatarsal is the second longest.
• Its triangular base has four articular facets for the lateral cuneiform, second, and fourth metatarsals.
• It gives origin to the second and third dorsal interossei and the first plantar interosseous.

Fourth Metatarsal Bone

• The base has a quadrilateral facet for the cuboid.
• It also articulates with the lateral cuneiform, third, and fifth metatarsals.
• It gives origin to the third and fourth dorsal interossei and the second plantar interosseous.

Fifth Metatarsal Bone

• The fifth metatarsal has a prominent tuberosity (styloid process) on its lateral side.
• The base articulates with the cuboid posteriorly and the fourth metatarsal medially.
• The plantar surface contains a groove for the abductor digiti minimi tendon.
• The peroneus brevis and peroneus tertius insert on the base, while the flexor digiti minimi brevis originates from its plantar surface.

Ossification of Metatarsal Bones

• Each metatarsal develops from one primary and one secondary ossification center.
• The primary ossification center forms the shaft.
• In the first metatarsal, the primary center appears during the 10th week of intrauterine life.
• In the second to fifth metatarsals, the primary centers appear during the 9th week of intrauterine life.
• The secondary ossification center appears at the base of the first metatarsal during the 3rd year of life.
• In the second to fifth metatarsals, the secondary centers appear at the heads between the 3rd and 4th years.
• All secondary centers fuse with the shaft by approximately 18 years of age.

Table 1.4.1: Differences between metacarpals and metatarsals

Feature	Metacarpals	Metatarsals
Head	Head is approximately equal in size to the base.	Head is smaller than the base, except in the first metatarsal.
Dorsal Surface of Shaft	Dorsal surface is flat and triangular.	Dorsal surface is smoothly convex without flattening.
Shaft	Shaft maintains a nearly uniform thickness throughout its length.	Shaft gradually tapers from the base toward the head.
Concavity of Shaft	Longitudinal concavity is directed anteriorly (palmarly).	Longitudinal concavity is directed inferiorly (plantarly).
Base	Base is irregular and is similar in size to the head.	Base is broader and larger than the head.

Table 1.4.2: Identification features of metatarsals

Metatarsal	Identification Features
First	Shortest, thickest, and stoutest metatarsal. The base bears a kidney-shaped articular facet for the medial cuneiform.
Second	Longest metatarsal. The base is wedge-shaped and has a triangular articular facet for the intermediate cuneiform.
Third	Second longest metatarsal. The base has a triangular articular facet for the lateral cuneiform.
Fourth	The base bears a quadrilateral articular facet for the cuboid.
Fifth	The base has a prominent tuberosity (styloid process) and a triangular articular facet for the cuboid.

Phalanges of Foot

• Each foot contains 14 phalanges: two in the great toe and three in each of the remaining toes.
• Compared with the fingers, the phalanges of the foot have shorter and smaller shafts.
• The great toe phalanges are thick, stout, and compressed from above downward.

General Features of Phalanx

Proximal Phalanx

• The base bears an oval articular facet. The head has a pulley-shaped articular surface. The shaft is flattened vertically and slightly concave.

Middle Phalanx

• The base has two articular facets. The head bears a pulley-shaped articular facet.

Distal Phalanx

• The distal phalanx is smaller than the proximal and middle phalanges. It has a broad base with articular facets. Its distal end is rough and non-articular, with a plantar tuberosity.

Phalanges of great toe

1. Extensor hallucis longus inserts on the dorsal surface of the distal phalanx.
2. Flexor hallucis longus inserts on the plantar surface of the distal phalanx.
3. Extensor digitorum brevis inserts on the dorsal surface of the proximal phalanx.
4. Abductor hallucis inserts on the medial side of the proximal phalanx.
5. Flexor hallucis brevis inserts on both sides of the proximal phalanx.
6. Adductor hallucis inserts on the lateral side of the proximal phalanx.

Phalanges of little toe

1. Abductor digiti minimi and flexor digiti minimi brevis insert on the lateral side of the proximal phalanx.
2. The third plantar interosseous inserts on the medial side of the proximal phalanx.
3. The fourth lumbrical inserts into the dorsal extensor expansion of the proximal phalanx.
4. Flexor digitorum brevis inserts on the plantar surface of the middle phalanx.
5. Extensor digitorum longus inserts on the middle and distal phalanges.

Phalanges of Second to Fourth toes

1. Extensor digitorum brevis inserts on the dorsal surface of the proximal phalanx.
2. Flexor digitorum brevis inserts on both sides of the plantar surface of the middle phalanx.
3. Extensor digitorum longus inserts on the middle and distal phalanges.
4. Flexor digitorum longus inserts on the plantar surface of the distal phalanx.

Ossification of Phalanges

• Each phalanx develops from one primary and one secondary ossification center.
• The primary ossification center forms the shaft.
  • Distal phalanx: Appears during the 9th week of intrauterine life.
  • Proximal phalanx: Appears during the 12th week of intrauterine life.
  • Middle phalanx: Appears during the 15th week of intrauterine life.

• The secondary ossification center forms the base of each phalanx.
  • Proximal phalanx: Appears during the 2nd year.
  • Middle phalanx: Appears during the 4th year.
  • Distal phalanx: Appears during the 8th year.

• The secondary centers unite with the shaft by approximately 18 years of age.

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