Competencies
- AN19.5: Describe the factors maintaining arches of foot with its importance.
- AN19.6: Explain the anatomical basis of flat foot and club foot.
INTRODUCTION
- The human foot is a highly specialized structure that plays an important role in standing, walking, running, jumping, and bearing body weight. It provides a stable base for the body while allowing smooth and efficient movement.
Functions of the Foot
The foot performs two major functions:
- Provides a flexible platform for body support: The foot supports the weight of the body while standing and walking. Its elastic, segmented arches distribute body weight evenly. These arches also help the foot adapt to uneven surfaces and absorb shock during movement.
- Acts as a lever for forward movement: The foot acts as a strong lever that helps propel the body forward during walking, running, and jumping. This function is made possible by the coordinated action of the long and short muscles of the foot.
Parts of the Foot
The skeleton of the foot is divided into three anatomical and functional parts:
- Hindfoot: Consists of the talus and calcaneus.
- Midfoot: Consists of the navicular, cuboid, and three cuneiform bones.
- Forefoot: Consists of the five metatarsals and fourteen phalanges.
Arches of the Foot
- The bones of the foot are arranged to form longitudinal and transverse arches. The concavity of these arches faces the plantar (sole) surface of the foot. This arched arrangement provides strength, flexibility, and efficient weight distribution.
- The weight-bearing areas of the foot can be assessed by examining a footprint, which shows the parts of the sole that come into contact with the ground.
- The factors that maintain these arches can be understood by comparing them to the structure of a stone bridge, where different components work together to provide strength and stability.
Classification of arches
The arches of the foot are classified into two main types:
1. Longitudinal Arches
The longitudinal arches run from the heel to the toes. They are of two types:
- Medial longitudinal arch
- Lateral longitudinal arch
2. Transverse Arches
The transverse arches run across the width of the foot. They are grouped into:
- Anterior transverse arch
- Posterior transverse arch
Structure of Arches of Foot
Medial Longitudinal Arch (MLA)
- The medial longitudinal arch is the higher and more mobile of the two longitudinal arches of the foot. It resembles a large arc of a small circle, making it well suited for shock absorption and adaptation to uneven ground.
Bones forming the medial longitudinal arch
The medial longitudinal arch is formed by:
- Medial part of the calcaneus
- Talus
- Navicular
- Three cuneiform bones
- First, second, and third metatarsals
Ends of the arch
The medial longitudinal arch has two ends:
Anterior end: Formed by the heads of the first, second, and third metatarsals.
Posterior end: Formed by the medial tubercle of the calcaneus.
Keystone
- The talus is the keystone of the medial longitudinal arch. It occupies the highest position and plays a major role in maintaining the stability of the arch.
Summit
- The summit is the highest point of the arch. It is formed by the superior articular surface of the body of the talus.
Pillars of the arch
The medial longitudinal arch is supported by an anterior pillar and a posterior pillar.
Anterior pillar:
- It is long and relatively weak. It is formed by the:
- Talus
- Navicular
- Three cuneiform bones
- First, second, and third metatarsals
Posterior pillar:
- It is short and strong. It is formed by the medial part of the calcaneus.
Main joint
- The talocalcaneonavicular joint is the principal joint of the medial longitudinal arch.
Lateral Longitudinal Arch (LLA)
The lateral longitudinal arch is lower and less mobile than the medial longitudinal arch.
It resembles a small arc of a large circle. This arch is more rigid and mainly provides stability and support during weight bearing.
Bones forming the lateral longitudinal arch
The lateral longitudinal arch is formed by:
- Lateral part of the calcaneus
- Cuboid
- Fourth and fifth metatarsals
Ends of the arch
- The lateral longitudinal arch has two ends:
- Anterior end: Formed by the heads of the fourth and fifth metatarsals.
- Posterior end: Formed by the lateral tubercle of the calcaneus.
Keystone
The cuboid is the keystone of the lateral longitudinal arch.
Summit
The summit is the highest point of the lateral longitudinal arch. It is formed by the articular facets on the superior surface of the calcaneus at the level of the subtalar joint.
Pillars of the arch
The lateral longitudinal arch is supported by an anterior pillar and a posterior pillar.
Anterior pillar:
It is long and relatively weak. It is formed by the:
Cuboid
Fourth metatarsal
Fifth metatarsal
Posterior pillar:
It is short and strong. It is formed by the lateral part of the calcaneus.
Main joint
The calcaneocuboid joint is the principal joint of the lateral longitudinal arch.
Factors Maintaining Longitudinal Arches
The longitudinal arches of the foot are maintained by structures that preserve their shape, provide elasticity, and allow them to withstand body weight during standing and walking.
The main factors maintaining the longitudinal arches are:
- Shape of the bones
- Ligaments that connect the bones (intersegmental ties)
- Muscles and tendons acting as slings
- Tie beams that prevent separation of the ends (pillars) of the arch
Factors maintaining the medial longitudinal arch
- Bones: the sustentaculum tali helps support the head of the talus, which is the keystone of the medial longitudinal arch.
- Ligaments: the following ligaments act as intersegmental ties and help maintain the arch:
- Spring (plantar calcaneonavicular) ligament, which supports the head of the talus.
- Interosseous ligaments between adjacent tarsal bones.
- Interosseous talocalcaneal ligament, which connects the talus and calcaneus.
- Muscles, tendons, and plantar aponeurosis
Sling action: The following tendons pull the summit of the arch upward and help maintain its height:
- Tibialis posterior
- Flexor hallucis longus
- Flexor digitorum longus
Tie beams: These structures prevent the anterior and posterior pillars of the arch from separating:
- Plantar aponeurosis
- Abductor hallucis
- Flexor hallucis brevis
Factors maintaining the lateral longitudinal arch
- Bones: The cuboid, which acts as the keystone, plays an important role in maintaining the lateral longitudinal arch.
- Ligaments: The lateral longitudinal arch is mainly supported by:
- Long plantar ligament
- Short plantar (plantar calcaneocuboid) ligament
- Muscles, tendons, and plantar aponeurosis
Sling action: The following tendons pull the summit of the arch upward:
- Peroneus (fibularis) brevis
- Peroneus (fibularis) tertius
- Peroneus (fibularis) longus
Tie beams: The following structures prevent separation of the pillars of the arch:
- Plantar aponeurosis
- Lateral part of flexor digitorum brevis
- Abductor digiti minimi
- Flexor digiti minimi
Table 17.1: Differences between medial and lateral longitudinal arches
| Feature | Medial Longitudinal Arch | Lateral Longitudinal Arch |
|---|---|---|
| Mobility and function | More mobile; acts as a shock absorber | Less mobile and more rigid; mainly transmits body weight |
| Shape | Large arc of a small circle | Small arc of a large circle |
| Anterior end | Heads of the first, second, and third metatarsals | Heads of the fourth and fifth metatarsals |
| Posterior end | Medial tubercle of the calcaneus | Lateral tubercle of the calcaneus |
| Summit | Superior articular surface of the talus | Superior surface of the calcaneus |
| Anterior pillar | Talus, navicular, three cuneiforms, and first three metatarsals | Cuboid, fourth metatarsal, and fifth metatarsal |
| Posterior pillar | Medial part of the calcaneus | Lateral part of the calcaneus |
| Main joint | Talocalcaneonavicular joint | Calcaneocuboid joint |
| Keystone | Head of the talus | Cuboid |
Table 17.2: Factors maintaining stability of medial and lateral longitudinal arches
| Supporting Structure | Medial Longitudinal Arch | Lateral Longitudinal Arch |
|---|---|---|
| Intersegmental ties | Spring (plantar calcaneonavicular) ligament | Long plantar ligament and Short plantar ligament |
| Tie beams | Plantar aponeurosisAbductor hallucisMedial part of flexor digitorum brevis | Plantar aponeurosisAbductor digiti minimiLateral part of flexor digitorum brevis |
| Slings | Tibialis posteriorFlexor hallucis longusFlexor digitorum longus | Peroneus (fibularis) longusPeroneus (fibularis) brevisPeroneus (fibularis) tertius |
Transverse Arches
- The transverse arches are the arches that run across the width of the foot in the coronal (transverse) plane.
- There are two transverse arches:
- Anterior transverse arch
- Posterior transverse arch
Anterior transverse arch
Bones forming the arch
- The heads of the five metatarsal bones form the anterior transverse arch.
Features
- The anterior transverse arch is a complete arch.
- Both ends of the arch, formed by the heads of the first and fifth metatarsals, come into contact with the ground during standing.
Posterior transverse arch
Bones forming the arch
- The posterior transverse arch is formed by:
- Most of the tarsal bones
- Bases of the metatarsal bones
Features
- The posterior transverse arch is an incomplete arch.
- Only the lateral part of the arch touches the ground.
- It forms half of a dome. When both feet are placed together, the posterior transverse arches of the two feet combine to form a complete dome.
Table 17.3: Comparison of anterior and posterior transverse arches
| Feature | Anterior Transverse Arch | Posterior Transverse Arch |
|---|---|---|
| Bones forming the arch | Heads of the metatarsal bones | Tarsal bones and bases of the metatarsal bones |
| Completeness | Complete arch | Incomplete arch that forms half of a dome |
| Bony factor | Rounded heads of the metatarsals | Wedge-shaped cuneiforms and bases of the metatarsals |
| Tie beams | Adductor hallucisDeep transverse metatarsal ligaments | Flexor hallucis brevisIntertarsal ligamentsTarsometatarsal ligaments |
| Slings | Peroneus (fibularis) longus and Tibialis posterior | Peroneus (fibularis) longus and Tibialis posterior |
Factors Maintaining Transverse Arches
The transverse arches of the foot are maintained by the shape of the bones, supporting ligaments, and the action of muscles and tendons.
- Bones
- Most of the tarsal and metatarsal bones are wedge-shaped. They are broader on the dorsal (superior) surface and narrower on the plantar (inferior) surface. This wedge-shaped arrangement helps form the plantar concavity of the transverse arches.
- Ligaments
- The superficial and deep transverse metatarsal ligaments help maintain the anterior transverse arch. The intertarsal and tarsometatarsal ligaments hold the adjacent tarsal and metatarsal bones together, providing additional support.
- Muscles and tendons
Tie beams
- The tendons of the peroneus (fibularis) longus and tibialis posterior act as tie beams to support the transverse arches.
Sling action
- The tendons of the tibialis anterior on the medial side and the peroneus (fibularis) brevis and peroneus (fibularis) tertius on the lateral side form a sling that helps maintain the transverse arches.
Intersegmental ties
- The dorsal interossei muscles hold the adjacent metatarsals together and provide additional support to the transverse arches.
Functions of Arches of Foot
The arches of the foot perform several important functions:
- Distribute body weight evenly across the foot.
- Absorb shock during standing, walking, and running.
- Act as elastic springs that help propel the body during walking, running, and jumping.
- Protect the blood vessels, nerves, and muscles of the sole by providing a concave plantar surface.
Role in weight transmission
- The arches distribute body weight throughout the bones of the foot. Body weight is transmitted from the tibia to the talus and then to the remaining bones of the foot.
Role in the walking cycle
- The medial longitudinal arch acts as the main shock absorber and helps propel the body forward during walking, running, and jumping. During the stance phase of walking, the forefoot pronates, causing the medial longitudinal and transverse arches to flatten slightly. This helps absorb shock. During the swing phase, the foot supinates, and the medial longitudinal arch rises again, making the foot more rigid for the next step. Thus, the arches of the foot provide both flexibility for shock absorption and rigidity for efficient forward movement.
CLINICAL INTEGRATION
- High-arched foot (pes cavus): Pes cavus is a deformity in which the longitudinal arches of the foot are abnormally high. Because of the exaggerated arches, body weight is concentrated on the heel and the forefoot. The person typically walks with hyperextension (dorsiflexion) of the metatarsophalangeal joints and flexion (plantar flexion) of the interphalangeal joints, giving the toes a clawed appearance. This abnormal weight distribution may cause pain and difficulty while walking.
- Hallux valgus (bunion): Hallux valgus is a deformity in which the great toe deviates laterally toward the other toes. It mainly affects the first metatarsophalangeal joint and is often associated with a bunion, which is an enlarged and inflamed bursa over the head of the first metatarsal. Although the exact cause is often unknown, prolonged use of tight, narrow, or high-heeled shoes is an important contributing factor. Patients may experience pain, swelling, and difficulty wearing footwear.
- Hammer toe: Hammer toe is a deformity in which one or more toes become bent, giving them a hammer-like appearance. It most commonly affects the second and third toes. The deformity is characterized by hyperextension of the metatarsophalangeal joint, flexion of the proximal interphalangeal joint, and hyperextension of the distal interphalangeal joint. This abnormal position may lead to pain, callus formation, and difficulty while walking or wearing shoes.
- Hallux varus: Hallux varus is a deformity in which the great toe deviates medially, away from the first metatarsal bone. It is less common than hallux valgus and may occur due to congenital abnormalities, trauma, or overcorrection during surgery for hallux valgus. The deformity can interfere with normal walking and may cause discomfort while wearing footwear.
- Hallux rigidus: Hallux rigidus is a condition characterized by painful stiffness of the first metatarsophalangeal joint. It usually develops as a result of degenerative arthritis, leading to the formation of bone spurs (osteophytes) that restrict movement of the great toe. Patients commonly experience pain during walking, reduced toe movement, and difficulty during the push-off phase of gait.
- Flat Foot (Pes Planus): Pes planus, or flat foot, is the most common deformity of the foot. It occurs when the longitudinal arches collapse or fail to develop, causing the entire or nearly the entire sole to come into contact with the ground. It is more commonly seen in children and females. The condition may result from congenital defects, arthritis, or weakness of structures that support the arch, such as the tibialis posterior tendon, spring ligament, or plantar aponeurosis. Patients often complain of foot pain, muscle fatigue, difficulty in walking, and a clumsy or shuffling gait due to loss of the foot’s normal spring action. Flattening of the arch may also compress nerves and blood vessels, leading to metatarsalgia. Treatment usually includes rest, strengthening exercises, arch-supporting footwear, and orthotic devices.
- Clubfoot (Talipes): Clubfoot (talipes) is a congenital or, less commonly, an acquired deformity in which the foot is abnormally rotated. The deformity may involve plantar flexion (equinus), dorsiflexion (calcaneus), inversion (varus), eversion (valgus), or a combination of these movements. Talipes equinovarus, in which the foot is plantar flexed, inverted, and adducted, is the most common type. Clubfoot can often be detected before birth by ultrasonography, while X-rays after birth help assess the severity of the bony deformity. Treatment depends on the type and severity of the condition and may include serial plaster casts, specially designed footwear, physiotherapy, and surgery in severe cases.
Important Questions
- Write a short note on medial longitudinal arch.
- List the factors maintaining longitudinal arches of foot.
- List the functions of arches of foot.
- Write a short note on pes planus.
- Write a short note on clubfoot.
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