Heel - Parts of the Foot
The foot is a part of vertebrate anatomy that supports the animal's weight while still allowing it to move about on the ground. The foot is one of the most complicated structures in the human body. It has over 100 moving parts, including bones, muscles, tendons, and ligaments, that allow the foot to balance the body's weight on just two legs and support a variety of activities.
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The Heel Bone and Largest Bone in the Foot
The calcaneus is the bone that makes up the foot's heel. It's one of the tarsals, which are the bones that make up the foot and ankle. The calcaneus is the largest bone in the foot, and it serves as the base for the rest of the tarsals and metatarsals. When running or walking, the calcaneus hits the ground with each step. Two of the most common causes of foot pain are stress fractures of the calcaneus and inflammation of the plantar fascia ligament, which is attached to the calcaneus.
Heel Anatomy/ Parts of the Heel
One of the seven tarsal bones that make up the foot is the calcaneus. The calcaneus is a short bone, which means it is about the same length as it is large. The tarsals are all known to be small bones. The calcaneus is the largest bone in the foot and the largest of all the tarsals.
Trabecular bone makes up the majority of the calcaneus (spongy bone). The strength of the calcaneus is proportional to its density of trabecular bone. Owing to the stresses exerted on the calcaneus by walking and running, runners and those with higher body weight gain more bone density in the calcaneus.
Structure of Heel Anatomy - Parts of the Heel
The calcaneus(heel body part) is a difficult bone to understand because it has so many different textures, attachments, and insertion points.
The posterior (back) portion is the heel. The Achilles tendon insertion point is on the superior aspect (top) of the posterior part of the calcaneus. There are two bursae (fluid-filled sacs that act as cushions) in front (internal) and behind (external) the insertion point for the Achilles tendon. The middle surface of the posterior portion of the calcaneus is the insertion point of the calcaneal tendon.
The talus, a tarsal bone above the calcaneus, attaches to the most superior part of the calcaneus. The anterior talar articular surface, the middle talar articular surface, and the largest, the posterior talar articular surface, all articulate with the calcaneus.
The calcaneus articulates with the cuboid bone, another tarsal bone, on its entire anterior (front) surface. Around the calcaneus, there are several additional processes (protuberances) that serve as channels and insertion points for other tendons, as well as assisting with balance.
An apophysis (growth plate) is found near the bulbous surface of the posterior calcaneus in childhood. About the age of 15, the apophysis solidifies, or fuses. 2 It doesn't solidify in certain females until they're 18 years old. It doesn't finish ossifying (hardening into strong bone) in some males until they're 22 years old.
Location - Heel Muscle Anatomy
The calcaneus (heel body part) is found at the back (posterior) of the foot, near the heel. The calcaneus will serve as a fulcrum point for flexion and extension of the foot because of its position. When you raise your toes off the floor as you're about to tap your foot, you're flexing. When you press down on the gas pedal, you're extending.
Anatomical Variations
In medical images, the calcaneus can be seen in a variety of anatomical variations. Some of these may be linked to specific medical conditions, while others may not cause any discomfort and are only noticed because radiologists often notice them.
A pseudofracture of the apophysis is a partly ossified apophyseal plate that looks like a fracture on an X-ray. This is a common calcaneus variation that does not need treatment.
A congenital tarsal coalition is a connection between the tarsals, most commonly the calcaneus and talus, that prevents the tarsals from properly articulating. Ossification (bone fusion), fibrous tissue, or cartilage buildup may all contribute to the alliance.
Calcaneal pseudocysts, also known as calcaneal pseudotumors, are common natural variations in calcaneus images caused by variations in bone density. Calcaneal pseudocysts are normally only seen in children and disappear as they get older.
A nutrient foramen (a hole that allows blood vessels to pass through) may form in the calcaneus' spongy bone. This is a natural but uncommon variation that is totally harmless.
Calcaneal Apophysitis
The most common cause of heel pain in children is calcaneal apophysitis. 6 It's an inflammation of the calcaneal apophysis brought about by repeated hits from running or jumping.
Bursitis
A bursa is a fluid-filled sac that serves as a buffer or bumper between potentially tender areas and irritated tissue. Bursitis is an inflammation of the bursae, which are usually located around the insertion points of tendons or between articulated tarsal bones such as the talus which is calcaneus and may cause heel or foot pain (talocalcaneal joint).
Plantar Fasciitis
The most common cause of heel and foot pain in adults is plantar fasciitis. 7 The plantar fascia tendon aids in maintaining the form of the foot's bottom (plantar surface). This widespread tendonitis affects many runners and is difficult to treat.
Stress Fractures
Stress fractures in the calcaneus may develop as a result of hitting the heel repeatedly. There are usually small cracks that cause foot pain. A stress fracture is rarely major, but since it is in the heel, it takes time to heal.
Avulsion Fractures
An avulsion fracture occurs when a tendon rips away from its insertion point. The tendon usually does not separate from the bone, but the bone to which it is attached may do so, hence the name.
The Achilles tendon and the plantar fascia tendon are the two main tendon insertion points on the calcaneus. Avulsion fractures are less common than Achilles tendon ruptures. The discomfort from a simple Achilles tendon rupture is felt more in the ankle or calf than in the heel.
FAQs on Heel
1. What is the heel, and what are its main anatomical components?
The heel is the posterior region of the foot, located directly below the ankle. Its primary structural component is the calcaneus, which is the largest bone in the foot. Key components include the calcaneus bone, a thick pad of subcutaneous fat that provides cushioning, and the insertion point for the Achilles tendon, which connects the calf muscles to the heel.
2. What is the primary function of the heel bone (calcaneus) in the human body?
The primary function of the calcaneus is to transmit the body's weight to the ground during standing and locomotion. It serves as a crucial foundation for the foot and acts as a strong lever for the calf muscles. This leverage, via the Achilles tendon, is essential for providing the propulsive force needed for movements like walking, running, and jumping.
3. What is a calcaneus fracture and what typically causes it?
A calcaneus fracture is a break in the heel bone. These are often severe and painful injuries that can impair mobility. The most common cause is a high-energy traumatic event that crushes the bone under the body's weight. Typical scenarios include:
- A fall from a significant height, landing on the feet.
- A major car crash.
Such impacts can cause the heel bone to widen, shorten, and become significantly deformed.
4. How does the Achilles tendon work with the heel to facilitate movement?
The Achilles tendon, the body's strongest tendon, connects the calf muscles (gastrocnemius and soleus) to the back of the calcaneus. When the calf muscles contract, they pull on this tendon. This action lifts the heel, causing the foot to point downwards in a motion called plantar flexion. This is the fundamental mechanism that allows us to push off the ground when we walk, run, or jump.
5. Why is the calcaneus one of the most frequently fractured tarsal bones?
The calcaneus is highly susceptible to fractures primarily because of its anatomical position and biomechanical role. During a fall from a height, it is often the first bone to absorb the impact of the landing. The axial load from the body's weight is driven from the tibia through the talus bone and directly into the calcaneus, creating immense force that can exceed the bone's structural capacity, leading to a fracture.
6. What is the difference between plantar fasciitis and Achilles tendonitis, two common causes of heel pain?
Although both conditions cause significant heel pain, they affect different anatomical structures and present with distinct symptoms.
- Plantar Fasciitis: This is an inflammation of the plantar fascia, a thick ligament on the bottom of the foot. The pain is typically a sharp, stabbing sensation on the underside of the heel, which is often most severe with the first steps in the morning.
- Achilles Tendonitis: This is an inflammation or irritation of the Achilles tendon itself. The pain is concentrated at the back of the heel where the tendon attaches, and it tends to worsen with physical activity rather than improve.
7. How does the heel's unique structure support bipedal locomotion in humans?
The robust structure of the human heel is a critical evolutionary adaptation for bipedalism. Its large, blocky shape provides a stable platform for bearing the entire body's weight. The arch of the foot, which originates from the calcaneus, functions as a natural shock absorber, dissipating forces during walking and running. This combination of stability and shock absorption, along with its role as a lever for propulsion, makes the heel essential for an efficient, upright human gait.
