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Human foot

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The bones of the human foot (from the dorsal view).

The Human foot is one of the most intricate structures in the human body. Consisting of 26 bones, 33 joints, and over 100 muscles, tendons, and ligaments, the foot is truly marvelous.[1] The intelligent design behind the foot is clearly displayed through its qualities and abilities. The human foot combines strength with intricacy, rigidity with a shock absorbing frame, and durability with fine motor flexibility. The foot is a testament to the ingenuity and genius of God’s creation.

Anatomy

Skeletal

The bones of the foot are divided into three parts: the forefoot, midfoot, and hindfoot.

This diagram depicts the bones of the foot (from the planter view).

Forefoot

The forefoot comprises of the five toes and the long bones that connect each of them to the foot. Each toe is formed out of multiple bones called phalanges. However, the number of bones in each toe varies. For the big toe, or the hallux, there are two phalanges and one joint, called the interphalangeal joint. Meanwhile, the other four toes each have three phalanges and two interphalangeal joints. The five toes are attached to the foot by five long bones called the metatarsals. The phalanges and metatarsals are joined together by the metatarsophalangeal joints, which are located on the balls of the feet. At the joint between the metatarsal and phalanx of the hallux, there are two additionally bones. These round bones are called the sesamoids.[2]

Midfoot

The midfoot consists of a five irregularly shaped bones: the cuboid bone, navicular bone, and the lateral, intermedial, and medial cuniform bones. These five bones form a pyramid-shaped structure, which forms the arch of the foot.[3] The arch serves as natural shock absorbers for the foot and is therefore vital to human mobility.[1] The bones of the midfoot connect to both the forefoot and hindfoot by means of intrinstic foot muscles (muscles within the foot) and the arch ligament (plantar fascia).

Hindfoot

The hindfoot contains both the heel and ankle of the foot. The heel consists of the calcaneus, which is the largest bone in the foot. This bone connects to the talus, which forms the ankle, by means of the subtalar joint. The top of the talus connects with the leg by supporting the tibia and fibula. This connection forms a hinge that allows for vertical foot motion. The hindfoot, connects with the midfoot by the ankle, or talus.[2]

Muscular

Intrinsic

This illustration depicts the muscles of the human foot.

There are twenty intrinsic muscles in the foot. These muscles work collaboratively to provide the foot with shape, support, and movement.[4] The muscles of the foot can be divided into three divisions: big toe muscles, smaller toe muscles, and central foot muscles.

Big toe muscles:

  • Abductor Hallucis
  • Flexor Hallucis Brevis
  • Adductor Hallucis

Smaller toe muscles:

  • Abductor Digiti Minimi
  • Flexor Digiti Minimi
  • Opponens Digiti Minimi

Central foot muscles:

  • Lumbricales
  • Quadratus Plantae
  • Flexor Digitorum Brevis
  • Dorsal Interossei
  • Plantar Interossei [1]

Extrinsic

Due to the size of the human foot, only so many muscles can physically exist the foot. Therefore, God placed the majority of the muscles that operate the foot outside of, or extrinsic of, the foot. By doing so, humans can retain their strength and mobility, while still having functionally sized feet.

With the exception of the popliteus, all muscles in the lower leg connect to the foot.[4] These muscles attach to the foot through tendons, which are non-elastic, dense regular connective tissue.[5] These tendons anchor to the elastic muscles, which, in turn, contract to move the lower leg and foot.[4] Of the muscles in the lower leg, these are the most likely to assist in the movement of the foot.

  • Tibialis Anterior
  • Extensor Digitorum Longus
  • Extensor Hallucis Longus
  • Peroneus Longus
  • Peroneus Brevis
  • Malleolus
  • Soleus
  • Gastrocnemius
  • Tibialis Posterior
  • Flexor Hallucis Longus
  • Flexor Retinaculum [1]

Movement

Plantar Flexion

Plantar flexion is the movement of raising the heels and balancing on the balls of the feet.[6] This action is preformed by contracting the intrinsic flexor muscles of the foot (for stability) and the extrinsic foot muscles located in the back of the leg (for power). The Achilles tendon, which connects the calf muscles to the heel, plays a pivotal role in this motion because it is the primary tendon connecting the leg muscles to the heel. Plantar flexion is important because it is necessary for walking, running, and pushing off surfaces with force.[4]

Dorsiflexion

Dorsiflexion is the opposite of planter flexion.[7] Instead of using the back leg muscles to raise the heel, plantar flexion raises the toes by contracting the muscles at the front of the leg. This motion also requires intrinsic extensor muscles because they curl the toes upward. Dorsiflexion is necessary for walking, running, and traversing inclined surfaces.[4]

Inversion

Inversion is the inward curling of the foot.

Eversion

Eversion is the opposite of inversion. It turns the foot outward.[8]

Pronation

Pronation is the natural inward motion of the foot as it lands on the ground and distributes the force of the impact throughout the foot. The act of pronation is vital to the health of the human foot because it mitigates the shock of motion (walking/running), which thereby provides the foot more protection and comfort. However, the arch of the foot has a dramatic effect on pronation. For example, while normally arched feet exhibit wonderful control over pronation, flat-footed and high-arched feet have a tendency to overpronate and underpronate, respectively. Overpronation and underpronation may lead to long-term health concerns.

Overpronation

Overpronation is when the foot rolls too far inward upon contact with the ground. By rolling the foot too far inward, the foot compromises the body’s stability and does not effectively dissipate the force of impact throughout the foot. Overpronation also inflict excessive stress upon the big toe because the overpronation cause the foot to launch off the ground from the inside of the front foot instead of from the middle.

Underpronation (Supination)

Underpronation, also known as supination, is the lack of pronation in the human gait. The insufficient roll of the foot in supination forces the outside of the foot to do the majority of the work. This places stress on the smaller outside bones, which will inevitably lead to foot complications such as plantar fasciitis and Achilles tendinits. These medical conditions will have a long-term affect on the health of the foot.[9]

Medical Issues

Conditions

A gout infection in the big toe of the foot.

Because the foot is comprised of a multitude of intricate bones, joints, muscles, and ligaments, it is often susceptible to stress, injury, infection, and other various health concerns. These medical conditions may be heredity, infectious, or self-induced. However, no matter the circumstances, it is important to understand the various medical issues surrounding the human feet, thereby insuring their wellbeing.

Bunions: Abnormal growths (of either bone or tissue) at the base of the toes (usually the big toes). This condition results in inwardly pointed toes, typically as a result of tight-fitting footwear or heredity deformity. Because bunions form on the bottom of the foot they are extremely painful.[10]

Calluses: Regions of thicker skin that build up as a result of frequent friction or pressure. Calluses provide extra protection to the body, however, they can, in some cases, cause discomfort.

Claw Toes: A joint condition in the toes, which is formed due to abnormal contractions. These contractions give the toes a claw-like appearance. Claw toes often form as a result of ill-fitting shoes.

Corns: Callus-like growths, which form into a pointed, or coned, shape. Also, like calluses, corns build up in regions of excess friction or pressure and can cause substantial discomfort.

Fallen Arches (Flat Feet): The arches of feet are flattened. This condition causes extra stress upon the foot and its joints. However, arch supports in footwear can relieve the stress of flat feet.[3]

Gout: A severely painful arthritic condition in which the joints of the toes (usually the big toes) become inflamed. Gout is due to the presence of uric acid crystals in the toe joints.[11]

Heel Spurs: Irregular bone growths in the heel of the foot due to excessive stress on the plantar fascia: the connective tissue responsible for shaping the arch of the foot and shock absorption. Over time, the body builds more bone to compensate for stress on the plantar fascia, thus creating bone spurs in the heel. These spurs can cause severe pain during standing and/or movement.[10]

Mallet Toes: A foot condition in which the toes constantly face downward because the interphalangeal joints cannot straighten out. Mallet toes can cause significant discomfort if not treated properly.

Metatarsalgia: Like the name suggests, metatarsalgia is a condition involving the metatarsals. Metatarsalgia is the inflammation of the metatarsophalangeal joints (commonly known as the balls of the feet). This condition can be attributed to poorly fitted shoes.[3]

Morton’s Neuroma: A build-up of tissue in the nerves located between the long bones of the foot (typically the third and fourth toe). This condition occurs when two juxtaposed bones begin to rub together, thereby pinching the nerve between them. Morton’s Neuroma causes inflammation and nerve sensations ranging from numbness to burning pain.[10]

Osteoarthritis: Like other forms of arthritis, osteoarthritis occurs as a result of age and lack of foot cartilage. Symptoms of osteoarthritis include inflammation, deformity, and discomfort.

Plantar Fasciitis: Swelling of the plantar fascia ligament as a result of overuse. This condition usually is sensed in the morning or after periods of rest. Syptoms of plantar fasciitis include inflammation and pain in the heel and/or arch of the foot.[3]

Rheumatoid arthritis: An autoimmune form of arthritis that creates antibodies to attack cells naturally produced within the body. This condition basically causes the body to damage its own joints. This type of arthritis causes stiffness, inflammation, and pain within the joints of the foot.[12]

Infections

Athlete’s Foot: A fungal infection of the feet that causes dry, flaky, and irritated skin. Athlete’s foot can be avoided by thoroughly washing and drying feet daily.

Diabetic Foot Infections: While diabetes does not cause infections, it does leave diabetics more susceptible to foot infections then the average human. Therefore, people with diabetes need to be consciously aware of symptoms that hint to infection or injury.

Nail Fungal Infection: A fungal infection of the toenails, which results in their discoloration as well as their crumbly texture.

Plantar Warts: Specific infection in the sole of the foot. This infection forms a callus with a centralized black spot. Because, they exist on the sole of the foot, plantar warts have the potential for pain. However, they are far more of a nuisance as they are very difficulty to remove.[3]

Injuries

An X ray image of a foot fracture.

The human foot can sustain a variety of injuries. However, two of the primary injuries are sprains and fractures.

Sprains

A foot sprain is an injury to the ligaments within the foot. Like tendons, ligaments are formed out of dense regular connective tissue [13] and are sprained when they are overstressed or torn. Symptoms of foot sprains include: inflammation, bruising, and pain. Treatment for foot sprains include: icing the swollen region, wrapping the foot, resting the foot, elevating the foot, and perhaps a splint or cast for supporting and protecting the foot. Of the various types of foot sprains, the most common, by far, is the angle sprain.

Fractures

The second, and more severe type of common foot injury is the fracturing of the foot. There are 26 bones in the foot and any of them can break. Symptoms of broken foot bones include swelling, bruising, and pain. The most common bones broken in the foot are the metatarsals, which are located in the forefoot. Depending upon the type and severity of the break patients may require a variety of treatments including foot casts and/or surgery. However, many metatarsal fractures do not require either. The anklebones are also commonly fractured. This type of break is more serious and almost always requires a protective cast and possibly surgery. Toe fractures (breaks in the phalangeal bones) also occur, but are less severe and do not require nearly as must medical attention. In come instance, the sesamoid bones in the big toe break or cause agitation substantial enough to merit their removal.[10]

Video

In this episode of eOrthopodTV, orthopaedic surgeon Randale C. Sechrest, MD narrates an animated tutorial of the anatomy of the foot.

References

  1. 1.0 1.1 1.2 1.3 Author Unknown. The Human Foot. Online University. Web. Accessed 11 February 2013.
  2. 2.0 2.1 Swierzewski, John J. Foot & Ankle Anatomy. Remedy Health Media. Web. 6 December 2011.
  3. 3.0 3.1 3.2 3.3 3.4 Author Unknown. Pain Management Health Center. WebMD. Web. 4 May 2010.
  4. 4.0 4.1 4.2 4.3 4.4 Swierzewski, John J. Muscles, Tendons & Ligaments of the Foot & Ankle. Remedy Health Media. Web. 1 March 2012.
  5. Wile, Jay L., and Shannon, Marilyn M. The Human Body: Fearfully and Wonderfully Made!. Cincinnati: Apologia Educational Ministries, Inc., 2001. Pg.48. Print.
  6. Wile, Jay L., and Shannon, Marilyn M. The Human Body: Fearfully and Wonderfully Made!. Cincinnati: Apologia Educational Ministries, Inc., 2001. Pg. 117. Print.
  7. Wile 117.
  8. Wile, Jay L., and Shannon, Marilyn M. The Human Body: Fearfully and Wonderfully Made!. Cincinnati: Apologia Educational Ministries, Inc., 2001. Pg. 118. Print.
  9. Author Unknown. Pronation. Runner’s World'. Web. Accessed 28 February 2013.
  10. 10.0 10.1 10.2 10.3 Author Unknown. Foot Pain & Problems. The Ohio State University Wexner Medical Center. Web. Accessed 26 February 2013.
  11. Author Unknown. Gout - Topic Overview. WebMD. Web. 12 November 2010.
  12. Author Unknown. Rheumatoid Arthritis - Overview. WebMD. Web. 14 April 2011.
  13. Wile, Jay L., and Shannon, Marilyn M. The Human Body: Fearfully and Wonderfully Made!. Cincinnati: Apologia Educational Ministries, Inc., 2001. Pg. 49. Print.