Feet

The feet are the terminal structures of the lower limbs, designed to support the body’s weight and facilitate locomotion. Each foot is composed of 26 bones, multiple joints, muscles, tendons, ligaments, and a network of blood vessels and nerves. The bones of the feet are divided into three main regions: the tarsals, metatarsals, and phalanges. These structures work together to provide stability, flexibility, and balance.

Location

The feet are located at the distal ends of the lower legs, extending from the ankles downward. They are positioned at the base of the body, making contact with the ground during standing, walking, and running.

Anatomy

The feet are highly specialized structures designed to support the body, facilitate movement, and adapt to various terrains. Their anatomy is intricate, involving bones, joints, muscles, tendons, ligaments, nerves, and blood vessels. Below is a detailed breakdown of the anatomy of the feet:

Bones of the Feet

Each foot contains 26 bones, divided into three main regions:

Tarsal Bones (7 bones)

Located in the posterior portion of the foot, forming the ankle and heel.

Calcaneus (Heel Bone):

• The largest tarsal bone.
• Forms the base of the heel and serves as the attachment point for the Achilles tendon.

Talus:

• Sits above the calcaneus and below the tibia and fibula.
• Articulates with the ankle joint, transmitting weight from the leg to the foot.

Navicular:

Positioned medially, articulating with the talus and cuneiform bones.

Cuboid:

Located laterally, articulating with the calcaneus and metatarsals.

Cuneiforms (Medial, Intermediate, Lateral):

Three small bones located medially, articulating with the navicular and the first three metatarsals.

Metatarsal Bones (5 bones)

• Long bones located in the middle region of the foot.
• Numbered 1 to 5, starting medially (big toe side).
• Provide structural support and serve as attachment points for ligaments and muscles.

Phalanges (14 bones)

• Located in the toes, with three phalanges for each toe (proximal, middle, distal) except the big toe, which has two (proximal and distal).
• The phalanges are shorter and smaller than the bones of the fingers.

Joints of the Feet

The feet contain numerous joints that allow for movement and adaptability:

Ankle Joint

• Formed by the talus and the distal ends of the tibia and fibula.
• Allows dorsiflexion and plantarflexion.

Subtalar Joint

• Located between the talus and calcaneus.
• Facilitates inversion and eversion of the foot.

Midfoot Joints

• Include the talonavicular and calcaneocuboid joints.
• These joints provide flexibility and adapt to uneven terrain.

Tarsometatarsal Joints (Lisfranc Joints)

Connect the tarsal bones to the metatarsals.

Metatarsophalangeal Joints (MTP Joints)

• Located between the metatarsal heads and the proximal phalanges.
• Allow flexion, extension, and limited abduction/adduction of the toes.

Interphalangeal Joints (IP Joints)

Found between the phalanges, allowing toe flexion and extension.

Arches of the Feet

The feet have three arches that provide support, absorb shock, and adapt to weight distribution:

Medial Longitudinal Arch

• Runs along the inside of the foot from the heel to the big toe.
• Formed by the calcaneus, talus, navicular, cuneiforms, and first three metatarsals.

Lateral Longitudinal Arch

• Runs along the outer edge of the foot from the heel to the fifth metatarsal.
• Formed by the calcaneus, cuboid, and fifth metatarsal.

Transverse Arch

Runs across the foot, formed by the metatarsal bases, cuboid, and cuneiform bones.

Muscles of the Feet

The muscles of the feet are categorized into two groups: extrinsic and intrinsic muscles.

Extrinsic Muscles

Originate in the leg and insert into the foot.

• Anterior Compartment: Includes the tibialis anterior, extensor hallucis longus, and extensor digitorum longus, responsible for dorsiflexion and toe extension.
• Posterior Compartment: Includes the gastrocnemius, soleus, tibialis posterior, and flexor digitorum longus, responsible for plantarflexion and toe flexion.
• Lateral Compartment: Includes the fibularis (peroneus) longus and brevis, responsible for eversion and support of the lateral arch.

Intrinsic Muscles

Located entirely within the foot, responsible for fine movements and arch support.

Dorsal Muscles: Extensor digitorum brevis and extensor hallucis brevis.

Plantar Muscles:

Organized into four layers:

• First Layer: Abductor hallucis, flexor digitorum brevis, abductor digiti minimi.
• Second Layer: Quadratus plantae, lumbricals.
• Third Layer: Flexor hallucis brevis, adductor hallucis, flexor digiti minimi brevis.
• Fourth Layer: Dorsal and plantar interossei.

Tendons and Ligaments

The tendons and ligaments provide structural integrity and facilitate movement:

Tendons

• Achilles Tendon: Connects the calf muscles to the calcaneus.
• Tibialis Posterior Tendon: Supports the medial arch.
• Peroneal Tendons: Stabilize the lateral side of the foot.
• Extensor and Flexor Tendons: Control toe movements.

Ligaments

• Plantar Fascia: A thick band of connective tissue supporting the medial arch.
• Deltoid Ligament: Stabilizes the ankle medially.
• Lateral Ligaments: Stabilize the ankle laterally, including the anterior talofibular, posterior talofibular, and calcaneofibular ligaments.

Nerves of the Feet

The nerves of the feet are branches of the sciatic nerve:

Tibial Nerve:

• Innervates the plantar surface of the foot.
• Branches into the medial and lateral plantar nerves.

Common Fibular (Peroneal) Nerve:

Divides into the superficial and deep fibular nerves, innervating the dorsal surface of the foot.

Sural Nerve:

Provides sensory innervation to the lateral side of the foot.

Blood Vessels of the Feet

The blood supply to the feet is provided by branches of the popliteal artery:

Posterior Tibial Artery

Divides into the medial and lateral plantar arteries, supplying the sole of the foot.

Dorsalis Pedis Artery

• Supplies the dorsal surface of the foot.
• Can be palpated on the dorsum of the foot for a pulse.

Venous Drainage

Superficial veins, such as the great and small saphenous veins, drain into the deep venous system.

Skin and Subcutaneous Tissue

Skin

• The plantar skin is thick and hairless, with a high density of sweat glands for grip and thermoregulation.
• The dorsal skin is thinner and more mobile.

Subcutaneous Fat

Provides cushioning, especially in weight-bearing areas like the heel and ball of the foot.

Function

The feet are essential for various activities, providing support, balance, and mobility. Their intricate structure allows them to bear the body’s weight, absorb shock, and adapt to different terrains. Below is a detailed explanation of the functions of the feet:

Support and Weight Bearing

The feet serve as the foundation for the body, supporting its entire weight during standing, walking, and other activities:

• The bones and arches distribute body weight evenly across the heel and forefoot.
• The structure of the feet ensures stability during static (standing) and dynamic (walking, running) activities.

Shock Absorption

The feet absorb and dissipate forces generated by body weight and external impacts:

Arches

• The medial and lateral longitudinal arches and the transverse arch act as natural shock absorbers.
• These arches compress slightly under pressure and rebound, reducing stress on the legs and spine.

Fat Pads

The thick subcutaneous fat in the heel and ball of the foot cushions impact during activities like running and jumping.

Balance and Stability

The feet play a vital role in maintaining balance and stability:

Dynamic Balance

• The feet adjust to changes in terrain and body movement, preventing falls and enabling smooth transitions between activities.
• Proprioceptive feedback from the feet helps coordinate balance with other parts of the body.

Static Balance

The feet stabilize the body during standing by evenly distributing weight and adjusting posture.

Locomotion

The feet facilitate various forms of movement, enabling locomotion through a combination of joints, muscles, and tendons:

Walking

The feet perform a heel-to-toe rolling motion during each step:

• The heel contacts the ground first (heel strike).
• The arch and midfoot roll forward.
• The toes push off the ground for the next step.

Running

• The feet transition from heel or midfoot contact to a powerful push-off using the toes, particularly the big toe.
• The arches store and release energy, improving efficiency.

Jumping and Landing

The feet generate force for upward propulsion during jumping and absorb impact upon landing.

Climbing

The toes and arches provide grip and adjust to uneven surfaces, allowing for secure climbing or ascending stairs.

Propulsion

The feet act as levers to propel the body forward or upward:

• Toes: The big toe plays a primary role in generating push-off force during walking or running.
• Achilles Tendon: Transfers force from the calf muscles to the foot, aiding in plantarflexion and propulsion.

Adaptation to Terrain

The feet adapt to various surfaces and conditions, ensuring stability and efficiency:

• Inversion and Eversion: Subtalar joint movements allow the foot to tilt inward (inversion) or outward (eversion), adapting to uneven surfaces.
• Flexibility: The numerous joints in the foot enable adjustments to slopes, rough terrain, or tight spaces.

Grip and Traction

The feet provide grip and traction to prevent slipping:

• Plantar Skin: The thick, textured skin of the sole enhances friction and grip, especially on slippery or uneven surfaces.
• Toe Movements: The toes assist in gripping objects or stabilizing the foot on irregular terrain.

Energy Storage and Release

The feet store and release elastic energy during movement:

The tendons, particularly the Achilles tendon and plantar fascia, stretch during weight-bearing and release stored energy during push-off, improving energy efficiency in walking and running.

Fine Motor Movements

The intrinsic muscles of the feet enable precise control and movements:

• Toe Movements: Flexion, extension, abduction, and adduction allow the toes to adjust position for stability or gripping objects.
• Arch Control: Intrinsic muscles maintain the arches, ensuring proper weight distribution.

Temperature Regulation

The feet play a role in thermoregulation through sweat glands:

• Sweat glands in the soles release moisture, aiding in cooling during physical exertion.
• The vascular network adjusts blood flow to the feet to regulate body temperature in hot or cold conditions.

Clinical Significance

The feet are essential for mobility and weight-bearing, making them prone to various injuries and medical conditions. Their clinical significance includes:

Injuries

• Fractures: Common in the metatarsals, tarsals, or phalanges due to trauma or stress.
• Sprains: Damage to ligaments, particularly around the ankle, from twisting or overuse.
• Plantar Fasciitis: Inflammation of the plantar fascia causing heel pain.

Structural Disorders

• Flat Feet: Loss of the medial arch, leading to instability or pain.
• High Arches: Excessive arch height, causing pressure on the ball and heel of the foot.

Circulatory Issues

• Peripheral Artery Disease (PAD): Poor blood flow to the feet, leading to pain or ulcers.
• Diabetic Foot Ulcers: A common complication in diabetes due to reduced sensation and impaired healing.

Neurological Conditions

Neuropathy: Often linked to diabetes, causing numbness or tingling in the feet.

Infections

Fungal infections like athlete’s foot or bacterial infections from cuts or wounds.