Functional Anatomy of the Foot

Original Editor - Ewa Jaraczewska

Top Contributors - Ewa Jaraczewska and Jess Bell  

Introduction

Human feet allow bipedal locomotion, and they are an essential sensory structure for postural control. The foot structure is complex, consisting of many bones, joints, ligaments and muscles. The foot is divided into three parts: rearfoot, midfoot, and forefoot. A clinician's ability to understand the anatomical structures of the foot is crucial for assessment and treatment, especially for clinicians working with clients with musculoskeletal conditions. This article discusses the key anatomical structures of the foot.

Key Terms

Axes: lines around which an object rotates. The rotation axis is a line that passes through the centre of mass. There are three axes of rotation: sagittal passing from posterior to anterior, frontal passing from left to right, and vertical passing from inferior to superior. The rotation axes of the foot joints are perpendicular to the cardinal planes. Therefore, motion at these joints results in rotations within three planes. Example: supination involves inversion, internal rotation, and plantar flexion.

Bursae: reduces friction between the moving parts of the body joints. It is a fluid-filled sac. There are four types of bursae: adventitious, subcutaneous, synovial, and sub-muscular.

Capsule: one of the characteristics of synovial joints. It is a fibrous connective tissue which forms a band that seals the joint space, provides passive and active stability and may even form articular surfaces for the joint.

Closed pack position: the position where there is the most congruency of the joint surfaces. In this position, joint stability increases. The closed pack position for interphalangeal joints is at full extension.

Degrees of freedom: the direction of joint movement or rotation; there is a maximum of six, including three translations and three rotations.

Ligament: fibrous connective tissue that holds the bones together.

Open (loose) pack position: position with least amount of joint congruency where joint stability is reduced.

Planes of movement: describe how the body moves. Up and down movements (flexion/extension) occur in the sagittal plane. Sideway movements (abduction/adduction) occur in the frontal plane. Movements in the transverse plane are rotational (internal and external rotation).

Foot Structure

The anatomical structure of the foot consists of the hindfoot, midfoot and forefoot. Each part of the foot is composed of several bones.

Bones and Articulations of the Foot

The foot's posterior aspect is called the hindfoot. The midfoot is located between the hindfoot and forefoot. The most anterior aspect of the foot is called the forefoot.

Area of the foot	Bones	Articulation	Characteristics	Key palpation points
Hindfoot	Talus Calcaneus	Subtalar joint (ST, talocalcaneal joint)	Three facets of the talus and the calcaneus are part of the ST joint	To find the calcaneus, palpate distally to the lateral malleolus. It is located directly under the talus. To locate the head of the talus, find medial and lateral malleoli. Place the thumb on the medial and your index finger on the lateral malleolus and move your fingers anteriorly. You feel a dip located behind the tendon. To verify that you are on the head of the talus, evert the patient's ankle while plantar flexed. You should feel the medial aspect of the head of the talus projecting into your contact.
Midfoot	Navicular Cuboid Medial cuneiform Intermediate (middle) cuneiform Lateral cuneiform	Midtarsal joint (MT, transverse tarsal joint, Chopart's joint) - formed from two smaller joints: Talocalcaneonavicular (TCN) Calcaneocuboid (CC)	The MT joint is located between the hindfoot and midfoot. The navicular articulates with all three cuneiform bones distally. The cuboid bone has a distal articulation with the base of the fourth and fifth metatarsal bones.	To palpate the navicular bone, the patient is supine, leg straight, and foot neutral. Find the bony prominence midway between the calcaneus and the base of the 1st metatarsal. The navicular bone extends in the lateral direction to the third metatarsal. To palpate the talocalcaneonavicular joint, the patient is supine or sitting. Find navicular bone. Move your finger proximal and lateral to the navicular bone's medial prominence to find the talonavicular joint's dorsal aspect. To palpate the medial cuneiform, the patient is supine. Start palpating from the great toe along the medial border of the foot until you reach the 1st metatarsal. The base of the 1st metatarsal flares. The medial (first) cuneiform is proximal to the 1st metatarsal. The intermediate (second) cuneiform approximates the second metatarsal. To find the lateral (third) cuneiform, palpate the shaft of the third metatarsal towards the ankle until the third metatarsal drops to the third cuneiform.
Forefoot	Metatarsals Phalanges Sesamoids	Tarsometatarsal joint (TMT or Lisfranc joint) Metatarsophalangeal joints (MTP joints) Proximal and distal interphalangeal joints (IP joints), except 1st toe (only one IP joint)	Digits 2-5 consist of a metatarsal and three phalanges. The 1st toe has only two phalanges. The metatarsals and corresponding phalanges create the forefoot's 5 rays. The joint can be divided in to three columns: medial column (first metatarsal and medial cuneiform articulation) the middle column (the second and third metatarsal articulation with intermediate and lateral cuneiform) the lateral column (the fourth and fifth metatarsal and cuboid articulation). The TMT joint connects the midfoot with the forefoot. It originates at the lateral, intermediate and medial cuneiforms articulating with the bases of the 1st, 2nd, and 3rd metatarsal bones. The bases of the 4th and 5th bones connect with the cuboid bone.	To palpate the shaft of the 5th metatarsal bone, the patient is sitting or supine. The foot is in a relaxed position. Palpate on the lateral side of the foot, superior to the cuboid bone. This is the attachment place for the interphalangeal joints of the foot. Palpate on the lateral side of the foot distal to the cuboid bone to fine the base (styloid process) of the 5th metatarsal bone. To find the head of the 5th metatarsal bone, place the talocrural joint in neutral and the phalanges in extreme extension. Palpate the distal end of the most lateral metatarsal. To palpate the sesamoids, position the patient supine, foot in the neutral position. Palpate distally along the medial longitudinal arch. Find the base of the 1st metatarsal bone and continue with palpation to the 1st metatarsophalangeal joint.

Foot Kinematics

Foot range of motion may vary between individuals based on specific activities that overload of the locomotor system. Foot range of motion is generally higher in women than men in younger age groups, but tends to even out in older adults. Physical activity may also influence gender- and age-related differences in range of motion.

Joint	Type of Joint	Plane of Movement	Motion	Kinematics	Closed pack position	Open pack position
ST joint	Condyloid	Mainly transverse	Inversion and eversion	Average range of motion (ROM) is: 30 degrees inversion / 18 degrees eversion	Full inversion	Inversion / plantarflexion
MT joint (Chopart's joint)	Talonavicular (TN) joint - Ball and socket CC joint - Modified saddle	Largely transverse;     Some sagittal	Inversion and eversion Dorsiflexion and plantarflexion Abduction and adduction	Inversion: approximately 8 to 10 degrees Eversion: between 2 and 3 degrees	TN: Full supination CC: Full supination	Midway between extreme range of motion
TMT joint (Lisfranc joint)	Plane synovial	Saggital	Dorsiflexion and plantarflexion	The mean ROM ranges from 22.4 to 33.5°. MTP 5 through 2 show increasing values	Full supination	Midway between supination and pronation
MTP joint	Condyloid	Sagittal, some Transverse	Dorsiflexion and plantarflexion Abduction and adduction	First MTP joint: maximum dorsiflexion ranges from 17 to 62 degreesAdduction ranges from 6 to 11 degrees	1st MTP: Hyperextension 2nd to 5th MTP: Maximum flexion	Slight (10 degrees) extension
IP joint	Hinge	Saggital	Flexion and extension	First IP joint: 70 degrees of extension and 45 degrees of flexion	Full extension	Slight flexion

Arches of the Foot

The foot arches:

• Support and protect the foot
• Redistribute pressure during dynamic loading
• Alter foot flexibility and rigidity

Lateral longitudinal arch: formed by the calcaneus, cuboid and the lateral two metatarsal bones

Medial longitudinal arch: formed by the calcaneus, talus, navicular, three cuneiforms and the medial three metatarsal bones

Transverse arch: runs across the tarsometatarsal joints

Foot Bursae

Bursae can be found in multiple locations at the foot: at the metatarsophalangeal joints, the base of the fifth metatarsal, and the back of the heel near the insertion of the Achilles tendon. Read more about bursae pathology here and here.

Ligaments of the Foot

The main function of the short and long plantar ligaments and the calcaneonavicular ligament (spring ligament) is to assist in passive arch maintenance.

Key Ligaments	Origin	Insertion	Action/Role	Palpation
Plantar Fascia	Medial calcaneal tubercle	Five metatarsal bones	Primary passive plantar tissue that supports the medial longitudinal arch	To locate the medial calcaneal tubercle, position the patient prone. Find the heel and come down into the medial aspect of the foot. Palpate the bony prominence.
Plantar calcaneonavicular ligament (SL, Spring ligament) Superomedial (SM) Lateral CN (LCN) Intermedial CN (ICN)	Anterior sustentaculum tali	Navicular (merges with a portion of the superficial deltoid ligament)	The passive stabiliser of the plantar arch in the talocalcaneal joint. Assists with preventing talus medial rotation and plantar flexion. Limits navicular dorsiflexion, eversion, and abduction.	To palpate the sustentaculum tali, position the patient supine, with their foot in neutral. Find the medial malleolus and palpate immediately inferior to the medial malleolus. The rigid structure under your finger is sustentaculum tali; from this point, only soft tissue (fat pad) can be palpated. To palpate the spring ligament, find the sustentaculum tali and navicular tuberosity. Place your thumbs on each of the bony prominences. In between the thumbs lies the spring ligament. To tighten the ligament, stretch the bones apart.
Calcaneocuboid ligament (CC): Medial CC (MCC) Dorsolateral CC (DLCC) Plantar CC (PCC)(short plantar ligament) Long plantar ligament (LPL)	DLCC: distal dorsolateral surface of the anterior process of the calcaneus PCC: anterior tubercle of calcaneus MCC: lateral band of the bifurcate ligament LPL: plantar aspect of the calcaneus	DLCC: proximal lateral surface of the cuboid bone PCC: the plantar surface of the cuboid posterior to the groove for the fibularis longus tendon LPL: cuboid ridge and basis of the 2nd to 5th metatarsals	Supports the medial and lateral longitudinal arches. Stabiliser of the calcaneocuboid joint and the midtarsal joint.	The patient is positioned supine to palpate the cuboid bone. The testing leg is internally rotated. Find the 5th metatarsal by palpating along the lateral border of the foot until you find the rounded edge of the tubercle of the 5th metatarsal. Find the calcaneus tubercule. The cuboid bone is located halfway between the tubercule of the 5th metatarsal and the calcaneal tubercule. It may be hard to palpate as extensor digitorum brevis covers it. The patient is supine to palpate the calcaneocuboid joint. With either hand, place the heel and the anterior portion of the rearfoot between your thumb and index finger. Next, induce varus stress and, with the tip of the thumb, palpate a lateral gap. This is the calcaneocuboid joint.
Lisfranc ligament	Lateral side of the medial cuneiform bone	Medial side of the base of the second metatarsal bone	Maintains the stability of the medial column and axial column of the foot arch

Muscles of the Foot

The dorsal muscles of the foot include: extensor digitorum brevis, extensor hallucis brevis

Muscle	Origin	Insertion	Innervation	Action
Extensor digitorum brevis	Calcaneus and inferior extensor retinaculum	Long extensor tendons of the medial four toes	Deep fibular nerve	Extension of the toes 2-5
Extensor hallucis brevis	Calcaneus and inferior extensor retinaculum	Base of the proximal phalanx of the great toe	Deep fibular nerve	Extension of the 1st toe

The plantar muscles of the foot lie within the central compartment between the muscles of the big and little toe, and they form the central surface of the foot sole:

• 1st layer: abductor hallucis, flexor digitorum brevis, abductor digiti minimi
• 2nd layer: quadratus plantae, lumbricals
• 3rd layer: flexor hallucis brevis, adductor hallucis, flexor digiti minimi brevis
• 4th layer: plantar and dorsal interossei

Muscle	Origin	Insertion	Innervation	Action
Abductor hallucis	Medial tubercle of the calcaneus, the flexor retinaculum and the plantar aponeurosis	Medial base of the proximal phalanx of the 1st toe	Medial plantar nerve (S2,S3)	Abduction and flexion of the 1st toe
Flexor digitorum brevis	Medial tubercle of the calcaneus and the plantar aponeurosis	Middle phalanges of the digits 2-5	Medial plantar nerve (S2,S3)	Flexion of the toes 2-5 at the proximal interphalangeal joints (PIP)
Abductor digiti minimi	Medial and lateral tubercles of the calcaneus and the plantar aponeurosis	Lateral base of the proximal phalanx of the 5th digit	Lateral plantar nerve (S1-S3)	Abduction and flexion of the 5th toe
Quadratus plantae	Calcaneus	Tendon of the flexor digitorum longus	Lateral plantar nerve (S1-S3)	Flexion of the toes 2-5, together with flexor digitorum longus
Lumbricals	Tendon of the flexor digitorum longus	Medial proximal phalanx and dorsal expansion of the extensor digitorum longus	Lumbrical 1: Medial plantar nerve (S2, S3); Lumbricals 2-4: Lateral plantar nerve (S2-S3)	Flexion at the metatarsophalangeal joints and extension at the interphalangeal joints
Flexor hallucis brevis	Lateral head – plantar surfaces of the cuboid and lateral cuneiforms Medial head – posterior tibialis tendon	The base of the proximal phalanx of the 1st toe	Medial plantar nerve (S2,S3)	Flexion of the 1st toe at the metatarsophalangeal joint
Adductor hallucis	Oblique head – the bases of the 2nd, 3rd, and 4th metatarsals Transverse head – the plantar ligaments of the metatarsophalangeal joints	Lateral aspect of the base of the proximal phalanx of the 1st toe	Deep branch of lateral plantar nerve	Adduction of the 1st toe Supports the transverse arch of the foot
Flexor digiti minimi brevis	The base of the fifth metatarsal	The base of the proximal phalanx of the fifth digit	Superficial branch of lateral plantar nerve	Flexion of the 5th toe at the metatarsophalangeal joint
Plantar and dorsal interossei	Plantar: medial side of metatarsals 3-5 Dorsal: lateral aspect of the metatarsals	Plantar: medial sides of the phalanges of digits 3-5 Dorsal: medial side of the proximal phalanx of the second digit and lateral sides of the proximal phalanxes of digits 2-4	Lateral plantar nerve	Plantar: Adduction of the lateral three digits and flexion at the metatarsophalangeal joints Dorsal: Abduction of the lateral four digits and flexion at the metatarsophalangeal joints

Innervation of the Foot

Nerve	Origin	Branches	Motor Fibres	Sensory Fibres
Plantar nerve	Tibial nerve at the medial malleolus	Medial plantar nerve (MPN) Lateral plantar nerve (LPN)	MPN: abductor hallucis, flexor digitorum brevis, and flexor hallucis brevis muscles. LPN: abductor and flexor digiti minimi, the adductor hallucis, and the interossei muscles.	MPN: sole innervation, 1st, 2nd and 3rd toes, often 4th toe. LPN: sole innervation, 5th toe, occasionally 4th toe.
Sural nerve	Tibial nerve and cutaneous branches of the common fibular nerve	Sural communication and lateral sural cutaneous nerve		Sensory innervation for the posterolateral aspect of the distal third of the leg and the lateral aspect of the foot, heel, and ankle

Vascular Supply of the Foot

Blood supply to the foot comes primarily from the anterior and posterior tibial arteries and the terminal branches of the popliteal artery.

Artery	Origin	Branches	Supply
Posterior tibial artery	Popliteal artery	Circumflex fibular artery Nutrient artery Muscular artery Communicating artery Perforating artery Medial malleolar artery Calcaneal artery Medial plantar artery Lateral plantar artery	Muscles of the sole of the foot
Anterior tibial artery	Terminal branch of the popliteal artery	Posterior and anterior recurrent tibial artery Muscular artery Perforating artery Anterior medial and lateral malleolar arteries Dorsalis pedis artery	Dorsal side of the foot
Medial plantar artery (MPA) and lateral plantar artery (LPA)	Posterior tibial artery	Plantar arch extending from the 1st to the 5th metatarsal	MPA supplies abductor hallucis muscle and flexor digitorum brevis muscle LPA supplies plantar aponeurosis between flexor digitorum brevis and abductor digiti minimi muscles
Sural artery	Popliteal artery	Lateral and medial branch	Supplies plantaris muscle

Clinical Relevance

1. Knee varus leads to a greater peak hindfoot eversion, and increases foot rigidity.
2. Dysfunction of the plantar fascia affects the height and shape of the medial longitudinal arch.
3. Pes planus may be produced by isolated spring ligament injuries. You can learn about orthotic solutions for foot pathologies here.
4. The calcaneocuboid ligament can be damaged during an inversion injury of the foot.
5. The transtarsal joint achieves stability through the bony shape, ligament tightness and extrinsic muscles crossing the foot as no intrinsic muscles attach to the talus or calcaneus and insert into the cuboid or navicular bones. This may be the cause of this joint's frequent hypermobility.
6. Hammer and claw toe deformities can be prevented with strong action of the interossei and lumbricals.
7. Increased tissue stiffness in gastrocnemius and hamstrings muscles can lead to plantar fasciitis, and calf muscle stretching can help solve this problem. This Plus programme discusses a new protocol for plantar heel pain syndrome.
8. Acute or chronic tears in the plantar fascia can be diagnosed by palpation of a painful lump on the sole of the foot. You can learn about the assessment of plantar heel pain here.
9. Gait pathology can result from decreased range of motion of the ankle and first metatarsophalangeal joints, which leads to limitation in joint mobility (LJM) of the foot joints. Learn more about lower leg and foot regional pain and gait deviations here.
10. "Obese individuals exhibit flatter feet, reduced inversion–eversion range of motion, and higher peak plantar pressures when walking".

Resources

• Golanó P, Vega J, de Leeuw PA, Malagelada F, Manzanares MC, Götzens V, van Dijk CN. Anatomy of the ankle ligaments: a pictorial essay. Knee Surg Sports Traumatol Arthrosc. 2010 May;18(5):557-69.
• Fraser JJ, Feger MA, Hertel J. MIDFOOT AND FOREFOOT INVOLVEMENT IN LATERAL ANKLE SPRAINS AND CHRONIC ANKLE INSTABILITY. PART 1: ANATOMY AND BIOMECHANICS. Int J Sports Phys Ther. 2016 Dec;11(6):992-1005
• Ghanem I, Massaad A, Assi A, Rizkallah M, Bizdikian AJ, El Abiad R, Seringe R, Mosca V, Wicart P. Understanding the foot's functional anatomy in physiological and pathological conditions: the calcaneopedal unit concept. Journal of Children's Orthopaedics. 2019 Apr;13(2):134-46.