Comprehensive Anatomy of the Foot and Ankle

Original Editor - Carin Hunter
Top Contributors - Jess Bell, Carin Hunter, Wanda van Niekerk, Uchechukwu Chukwuemeka, Kim Jackson and Olajumoke Ogunleye

Basic Structure of the Foot and Ankle

The ankle or tibiotalar joint constitutes the junction of the lower leg and foot. The osseous components of the ankle joint include the distal tibia, distal fibula, and talus.

The  anatomic structures below the ankle joint comprise the foot, which includes:

1. Hindfoot: The hindfoot is the most posterior aspect of the foot. It is composed of the talus and calcaneus, two of the seven tarsal bones. The talus and calcaneus articulation is referred to as the subtalar joint, which has three facets on each of the talus and calcaneus.
2. Midfoot: The midfoot is made up of five of the seven tarsal bones: navicular, cuboid, and medial, middle, and lateral cuneiforms.  The junction between the hind and midfoot is termed the Chopart's joint, which includes the talonavicular and calcaneocuboid joints.
3. Forefoot: The forefoot is the most anterior aspect of the foot. It includes metatarsals, phalanges (toes), and sesamoid bones. Each digit has a metatarsal and three phalanges, apart from the great toe, which only has two phalanges. The articulation of the midfoot and forefoot forms the Lisfranc joint.

Bones

The bones of the ankle are named as follows:

• Tibia
• Fibula

The bones of the foot are named as follows:

• Tarsals
  • Talus, calcaneus, navicular, cuboid, cuneiforms (medial, intermediate and lateral)

• Metatarsals
  • Numbered from medial or first (big toe), to lateral or fifth (little toe)

• Phalanges
  • Toes 2-5 each have 3 phalanges. The first or big toe (hallux) has only two

Joints

Joint	Type of Joint	Plane of Movement	Motion
Talocrural joint	Hinge	Sagittal	Dorsiflexion & Plantarflexion	Formed between the distal tibia-fibula and the talus, and is commonly known as the ankle joint. The distal and inferior aspect of the tibia – known as the plafond – is connected to the fibula via tibiofibular ligaments forming a strong mortise which articulates with the talar dome distally.
Subtalar joint (Talocalcaneal joint)	Condyloid	Mainly transverse Some sagittal	Inversion & Eversion Dorsiflexion & Plantarflexion	Formed between the talus and calcaneus. There are three facets on each of the talus and calcaneus. The posterior subtalar joint constitutes the largest component of the subtalar joint. The subtalar joint allows inversion and eversion of ankle and hindfoot.
Midtarsal joint (Transverse tarsal joints or Chopart’s joint)	Talonavicular joint - Ball and socket Calcaneocuboid joint - Modified saddle	Largely in transverse     Some sagittal	Inversion & Eversion Flexion & Extension	It is an S-shaped joint when viewed from above. It consists of two joints – the Talonavicular Joint and Calcaneocuboid Joint.
Talonavicular joint	Ball and socket	Largely in transverse	Inversion & Eversion	Formed between the anterior talar head and the concavity on the navicular. It does not have its own capsule, but rather shares one with the two anterior talocalcaneal articulations.
Calcaneocuboid joint	Modified saddle	Sagittal	Flexion & Extension	Formed between the anterior facet of the calcaneus and the posterior cuboid. Both articulating surfaces, present a convex and concave surface with the joint being convex vertically and concave transversely. Very little movement occurs at this joint.
Tarsometatarsal joint (Lisfrank Joint)	Planar			The distal tarsal rows including the three cuneiform bones and cuboid articulate with the base of each metatarsal to form the TMT complex. It is an S-shaped joint and is divided into 3 distinct columns: Medial – composed of 1st metatarsal and medial cuneiform. Middle – composed of 2nd and 3rd metatarsals, intermediate and lateral cuneiforms respectively. Lateral – composed of 4th and 5th metatarsals and the cuboid.
Metatarsophalangeal joint	Condyloid	Sagittal Some Transverse	Flexion & Extension Abduction & Adduction	Formed between the metatarsal heads and the corresponding bases of the proximal phalanx.
Interphalangeal joint	Hinge	Sagittal	Flexion & Extension	Formed between the phalanges of the toes. Each toe has proximal and distal IP joints except for the great toe which only has one IP joint.

Ligaments

Ankle ligament injury is the most frequent cause of acute ankle pain. Hence, it is important to understand the anatomy of ankle ligaments for correct diagnosis and treatment.

The ligaments around the ankle can be divided, depending on their anatomic position, into three groups: the lateral ligaments, the deltoid ligament on the medial side, and the ligaments of the tibiofibular syndesmosis that join the distal epiphyses of the tibia and fibula.

The lateral collateral ligament complex (LCL) consists of:

1. Anterior talofibular ligament: it is the most frequently injured ligament of the ankle. This ligament plays an important role in limiting anterior displacement of the talus and plantar flexion of the ankle.
2. Posterior talofibular ligament: The posterior talofibular ligament originates from the malleolar fossa, located on the medial surface of the lateral malleolus, coursing almost horizontally to insert in the posterolateral talus. It is the strongest ligament of the lateral ankle. plays only a supplementary role in ankle stability when the lateral ligament complex is intact.
3. Calcaneofibular ligament: The calcaneofibular ligament originates from the anterior part of the lateral malleolus. Its primary role is to restrain inversion in a neutral or dorsiflexed position, restrains subtalar inversion, thereby limiting talar tilt within the ankle mortise.

The medial collateral ligament (MCL), also known as Deltoid ligament, is composed of two layers; superficial and deep. The MCL is a multifascicular ligament, originating from the medial malleolus to insert in the talus, calcaneus, and navicular bone. It primarily restrains valgus tilting of the talus. Both the superficial and deep layers individually resist eversion of the hindfoot. It also stabilises ankle against plantar flexion, external rotation, and pronation.

The ligaments of the tibiofibular syndesmosis consist of anterior or anteroinferior tibiofibular ligament, the posterior or posteroinferior tibiofibular ligament, and the interosseous tibiofibular ligament. The syndesmotic ligament complex ensures the stability between the distal tibia and the fibula and resists the axial, rotational, and translational forces that attempt to separate the tibia and fibula.

LIGAMENT	DESCRIPTION	PROXIMAL ATTACHMENT	DISTAL ATTACHMENT	FUNCTION
Anterior Talofibular Ligament (ATFL)	Flat weak band that extends anteriomedially. Most commonly damaged ligament of the ankle.	Lateral Malleolus	Neck of Talus	Restrains anterior displacement of the talus in respect to the fibula and tibia. Resists inversion in plantarflexion.
Posterior Talofibular Ligament (PTFL)	Thick, a fairly strong band that runs horizontally medially. This ligament is under greater strain in full dorsiflexion of the ankle. Rarely injured because bony stability protects ligaments when ankle is in dorsiflexion.	Malleolar Fossa of Fibula	Lateral Tubercle of Talus	Forms the back wall of the recipient socket for the talus' trochlea. Resists posterior displacement of the talus.
Calcaneofibular Ligament (CFL)	Round cord that passes posteroinferior	Tip of Lateral Malleolus	Lateral Surface of Calcaneus	Aids Talofibular stability during Dorsiflexion. Restrains inversion of the calcaneus with respect to the fibula. Prevents Talar tilt into Inversion.

LIGAMENTS	DESCRIPTION	PROXIMAL ATTACHMENT	DISTAL ATTACHMENT	FUNCTION
Anterior Tibiotalar Ligament		Medial Malleolus	Head of Talus	Reinforces Ankle Joint. Control Plantarflexion & Eversion
Posterior Tibiotalar Ligament			Talus Posteriorly	Controls Dorsiflexion
Tibionavicular Ligament	Forms most anterior part of the Deltoid Ligament		Dorsomedial Aspect of Navicular	Reinforces Ankle Joint
Tibiocalcaneal Ligament	Very thin ligament		Sustentaculum Tali	Reinforces Ankle Joint

Muscles of the Foot

Extrinsic Foot Muscles

These muscles have contractile portions that lie outside the ankle, in the leg, and the tendons of those muscles insert onto the bones of the foot in such a way that ankle motion occurs when the muscles contract.

There are four 4 compartments, separated by fascia:

1. Superficial Posterior compartment (Plantar Flexors)
   1. Gastrocnemius (TA)
   2. Soleus (TA)
   3. Plantaris
2. Deep posterior compartment (Plantar Flexors)
   1. Flexor Hallucis Longus (inversion) (plantar surface of 1 toe)
   2. Flexor Digitorum Longus (inversion) (plantar surface 2-5 toes)
   3. Tibialis Posterior (inversion) (navicular, medial cuneiform, 2-4 toes, other cuneiforms, cuboid)
3. Lateral compartment (Plantar Flexors)
   1. Peroneus Longus (eversion, PF first metatarsal) (medial cuneiform and 1 toe)
   2. Peroneus Brevis (eversion)  (5 toe)
4. Anterior compartment (Dorsiflexors)
   1. Tibialis anterior (inversion) (1 toe, medial cuneiform)
   2. Extensor Hallucis Longus (inversion)
   3. Extensor Digitorum Longus
   4. Posterior Tibialis (eversion)

The dorsum of the foot has only one muscle (maybe 2 depending on classification). This is the extensor digitorum brevis (some authors name the most medial part of this muscle extensor hallucis brevis). Tendons are the main collagenous structures in the dorsum. The tendons connect the anterior/dorsiflexor compartment muscles of the leg to the foot bones.

MUSCLE	ACTION	PROXIMAL ATTACHMENT	DISTAL ATTACHMENT	INNERVATION
POSTERIOR COMPARTMENT
SUPERFICIAL POSTERIOR COMPARTMENT
Gastrocnemius	Plantarflexion when Knee Extended Flexion Knee Raises Heel during Walking	Lateral Head: Lateral Aspect of Lateral Femoral Condyle Medial Head: Popliteal Surface of Femur Superior to Medial Femoral Condyle	Posterior Surface Calcaneus via Calcaneal Tendon (Achilles Tendon)	Tibial Nerve S1-S2
Soleus	Plantarflexion Steadies Leg on Foot	Posterior Aspect of Head Fibula Superior ¼ Posterior Surface Tibia Soleal Line & Medial Border Tibia
Plantaris	Weakly Assists Gastrocnemius in Plantarflexion	Inferior end Lateral Supracondylar Line of Femur Oblique Popliteal Ligament
DEEP POSTERIOR COMPARTMENT
Tibialis Posterior	Plantarflexion Inversion Supports Medial Longitudinal Arch	Interosseous Membrane Posterior Surface Tibia inferior to Soleal Line Posterior Surface Fibula	Navicular Tuberosity Cuneiform Cuboid Bases of Metatarsals 2-4	Tibial Nerve L4-L5
Flexor Digitorum Longus	Plantarflexion Flexion Lateral Four Digits Supports Longitudinal Arch	Medial Part Posterior Surface Tibia inferior to Soleal Line Broad Tendon to Fibula	Base Distal Phalanges Digits 2-4	Tibial Nerve S2-S3
Flexor Hallucis Longus	Weak Plantarflexion Flexion Big Toe at all Joints Supports Medial Longitudinal Arch	Inferior 2/3 Posterior Surface Fibula Inferior Part Interosseous Membrane	Base Distal Phalanx of Big Toe
LATERAL COMPARTMENT
Peroneus Brevis	Weak Plantarflexion Eversion	Inferior 2/3 of Lateral Surface Fibula	Dorsal Surface Tuberosity of Base 5th Metatarsal	Superficial Peroneal Nerve (Superficial Fibular Nerve) L5 - S2
Peroneus Longus	Weak Plantarflexion Eversion Supports Transverse Arch	Head & Superior 2/3 of  Lateral Surface Fibula	Base 1st Metatarsal Medial Cuniform
ANTERIOR COMPARTMENT
Tibialis Anterior	Dorsiflexion Inversion Supports Medial Longitudinal Arch	Lateral Condyle Tibia Superior ½ Lateral Surface Tibia Interosseous Membrane	Medial & Inferior Surfaces Medial Cuniform Base of 1st Metatarsal	Deep Peroneal Nerve (Deep Fibular Nerve) L4-L5
Extensor Digitorum Longus	Dorsiflexion Extends Lateral Four Digits	Lateral Condyle Tibia Superior ¾ Anterior Surface Interosseous Membrane	Middle & Distal Phalanges of Lateral Four Digits	Deep Peroneal Nerve (Deep Fibular Nerve) L5-S1
Extensor Hallucis Longus	Dorsiflexion Extends Big Toe	Middle Part Anterior Surface Fibula Interosseous Membrane	Dorsal Aspect of Base Distal Phalanx of Big Toe
Peroneus Tertius	Dorsiflexion Aids Eversion	Inferior 1/3 Anterior Surface Fibula Interosseous Membrane	Dorsum Base 5th Metatarsal

Intrinsic Foot Muscles

The plantar aspect of the foot contains the tough fibrous plantar aponeurosis covering muscles and tendons arranged in 4 layers, numbered from 1 superficial to 4 deep:

1. Layer 1
   1. Abductor digiti minimi,
   2. Flexor digitorum brevis
   3. Abductor hallucis
2. Layer 2
   1. Quadratus plantae
   2. Lumbricals
   3. Long tendons of flexor digitorum longus and flexor hallucis longus
3. Layer 3
   1. Flexor hallucis brevis,
   2. Adductor hallucis and
   3. Flexor digiti minimi brevis
4. Layer 4
   1. Interosseous muscles
   2. Long tendons of peroneus/fibularis longus and tibialis posterior

Arches

The arches of the foot provide force absorption, a base of support and act as a rigid lever during gait propulsion. There are three arches of the foot: the medial longitudinal arch, lateral longitudinal arch and transverse arch.

1. Medial Longitudinal Arch (MLA)
   • The longest and highest of all the arches. Bony components of MLA include the calcaneus, talus, navicular, the three cuneiform bones and the first three metatarsals. The arch consists of two pillars: the anterior and posterior pillars. The anterior pillar consists of the head of first three metatarsal heads and the posterior pillar consists of the tuberosity of the calcaneus. The plantar aponeurosis forms the supporting beam connecting the two pillars. The apex of the MLA is the superior articular surface of talus. In addition to the plantar aponeurosis, the MLA is also supported by the spring ligament and the deltoid ligament. The Tibialis anterior and posterior muscles play an important role in raising the medial border of the arch, whereas Flexor hallucis longus acts as a bowstring.  
2. Lateral Longitudinal Arch (LLA)
   • The lowest arch. Its bony components are the calcaneus, cuboid, fourth and fifth metatarsals. Like the MLA, the posterior pillar consists of the tuberosity of the calcaneus. The anterior pillar is formed by the metatarsal heads of 4th and 5th metatarsals. The plantar aponeurosis, long and short plantar ligaments provide support to the LLA. The Peroneus longus tendon plays an important role in maintaining the lateral border of the arch.
3. Transverse Arch
   • Concave in non-weight bearing and runs medial to lateral in the midtarsal and tarsometatarsal area. The bony component of the arch consists of the metatarsal heads, cuboids and three cuneiform bones. The medial and lateral pillars of the arch is formed by the medial and lateral longitudinal arch respectively. The arch is maintained by the Posterior tibialis tendon and the Peroneus longus tendon which cross the plantar surface from medial to lateral and lateral to medial respectively.