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Readers familiar with my previous books may be tempted to skip these introductory chapters Our understanding of the anatomy of the foot has not changed in the past few years, but it is worthwhile to review the information. When we get to the major themes of this book-prevention and treatment of specific foot and leg problems-then it will all make sense.
Many of my patients complain about the size and shape of their feet: They are either too big or too small, too wide or too narrow, too thick or too thin, or just plain fat and ugly. I have never understood why so many people hate their feet, or the feet of others. Even medical professionals voice such opinions. I once asked a doctor friend, "Just what is so disgusting about the human foot?"
"The size, shape, overall design, everything," he replied smugly. "It's total imperfection. But I guess that's why you chose podiatry. You must be making a fortune treating all those problems caused by bad feet."
I thought about his remarks for a few moments, thenbegan to explain just how functional the foot really is. "First of all," I replied, "the foot has to act as a lever to propel the body." I then pointed out to him that the foot has to be flexible, and it must be able to turn in or out. It must also provide balance so that its owner doesn't keep falling over.
So my patients often dislike their "ugly" feet, and my medical colleagues tend to view the foot with disdain. All the more reason for me to put the foot on a pedestal and to convince people to put aesthetics aside and learn how the foot functions and why it is shaped the way it is.
A foot is, or ought to be, the most dependable form of transportation you have, and it can often be an excellent barometer of your general physical condition. Imagine that your body is a finely tuned automobile, and that your feet are the wheels. (In fact, athletes often refer to their lower extremities as "wheels.") If your wheels are out of alignment, your total performance suffers. Conversely, as you will see in later chapters, trouble elsewhere in your body can manifest itself in your feet.
We will return to the analogy of your body as a machine later, but first I want to illustrate, in words and with diagrams, the anatomy of the foot-the bones and joints, the muscles and tendons, the ligaments, cartilage, blood vessels, and nerves. Once I have dealt with the parts of the foot, I will proceed to illustrate in the next chapter how they all work together to enable you to walk, run, jump, dance, play, or do whatever else you wish while on your feet.
A Quick Course in Anatomy
A human foot, ugly or beautiful, is not always 12 inches long. Foot size in a normal, healthy adult can range from 4 1/2 inches long by 3 inches wide (11 x 8 cm) to 24 inches long by 9 inches wide (61 x 23 cm). In most cases feet are made to order for your particular body shape and size. Exceptionally tall women often complain to me about their difficulty in finding attractive shoes to fit what they consider to be huge, unattractive feet. However, these women would look very silly with size 5 or 6 feet. Moreover, they would be unable to balance themselves properly, and would probably blow over in high winds. I advise these women to complain to shoe designers and manufacturers for satisfaction, rather than complaining about their fate.
Medical geniuses long ago divided the foot into three distinct parts: the forefoot, from the tips of the toes to the base of the metatarsals (the five bones that connect the midfoot and rearfoot bones to the toe bones); the midfoot, including the cuneiform, cuboid, and navicular bones; and the rearfoot, including the talus (ankle) and calcaneus (heel) bones (see Figure 1.1). Many people refer to the "ball" of the foot and the "arch" without knowing exactly where they are located. The ball is considered to be in the forefoot-on the bottom of the foot, under the metatarsal heads. The arch is generally considered to be in the midfoot area.
It is an interesting fact, at least to me, that over 95 percent of all foot surgery is done on the forefoot. However, these days many foot problems occur in the heel and ankle areas. I will explain why in various chapters throughout the book, but if you guess that it has to do with baby boomers who have been subjecting their bodies to stressful athletic endeavors for years, you will have hit the nail on the head.
You may be surprised to learn that a quarter of all the bones in the human body are in the feet. The normal foot has twenty-six bones of varying sizes and shapes (see Figure 1.1), plus two sesamoids, which lie underneath the first metatarsal. However, it is not uncommon for a person to have small extra bones called accessory ossicles. These extra bones are thought to be hereditary, and seldom cause any trouble. For anyone to have too few bones in the foot would be a medical rarity.
Bones and biomechanics go together, as you will learn in the following chapter. Getting back to our analogy of the body as a machine, you know that when one cog in a wheel is misshapen, the wheel, and hence the machinery, will malfunction. The same holds true for the foot when one of its bones is defective. An abnormal bone can lead to a biomechanical fault.
But before we get to biomechanical details, we have to examine other parts of the foot: the joints; all the soft tissues that hold the bones and joints in place and facilitate their movement, such as muscles, tendons, cartilage, and ligaments; the supply system that lubricates and nourishes the bones and soft tissues; and the electrical, or nerve, system that transmits signals to and from the brain, telling the feet when and where to go.
Two or more bones that come together articulate to form a joint. We hear a great deal about joints when we discuss arthritis and cartilage problems, and they can be a terrible pain at times. But without joints we would be quite inflexible, because most of them move, at least slightly, to allow our bodies to assume different postures and motions.
The joint in the foot that you probably think about most is the ankle joint, which connects the lower part of the leg to the back of the foot. It is a hinge-type joint in that its motion resembles that of a door opening. When you damage an ankle joint, walking or running becomes a nightmare because of the pain that occurs when weight is placed on the foot. Your gait can become exaggerated as you attempt to compensate by forcing most of the weight onto the other foot during the walking cycle. As a result, the biomechanics of both feet can be adversely affected.
A more crucial joint affecting the biomechanics of the foot during walking or running is the subtalar joint. It comprises three different articulations between the top surface of the heel bone and the bottom surface of the ankle bone. As you will see in the following chapter, when a person pronates (rolls from the outside of the heel inward) abnormally, the subtalar joint does not move as it should. If this occurs, a chain reaction develops and problems can occur throughout the foot.
The midtarsal joint, in the arch area of the foot, works together with the subtalar joint to help the foot compensate for a biomechanical fault, particularly a temporary one. This could occur when walking or running on uneven terrain or when upper-body motion changes-for example, when an athlete or a dancer assumes an unusual position. When the subtalar and midtarsal joints cannot compensate adequately for a more long-lasting biomechanical fault, the result could be a foot disorder. The subtalar joint used to be blamed for such disorders, but since computer and camera techniques that measure foot motion have become so much better in the past four years, we now know that the midtarsal joint is the leading culprit in forefoot compensation.
People are unlikely to suffer to any great extent from subtalar or midtarsal joint pain. However, one other type of joint in the foot can cause excruciating pain at times: the metatarso-phalangeal joint. Five of these joints are formed by articulation of the heads of the metatarsal bones (in the ball area of the foot) and the ends of the proximal phalanges (the large bones in the toes). These joints can be seen in Figure 1.2.
For reasons that I will describe in subsequent chapters, the big-toe joint-where the proximal phalanx (the big bone of the first, or great, toe) and the metatarsal head come together-often bears the brunt of unequal weight distribution that a biomechanical fault inflicts on the foot. As a result, this joint is subjected to a lot of added wear and tear that makes it susceptible to osteoarthritis and similar conditions. Gout may also affect the big-toe joint, but this is not caused by a biomechanical problem. As you will discover in Chapter 10, gout is a disease that can be controlled by proper medication and diet.
Although there are many other joints in the foot, our major concern in this book is the four joints mentioned above, because they are the ones that most affect, and are affected by, biomechanical foot faults. However, it is not uncommon to have problems with the interphalangeal joints, which lie between the phalanges, or toe bones, in the various toes (two bones comprise the big toe, and all the other toes have three bones). When I discuss forefoot pain in Chapter 4, I will deal with conditions that can affect these phalangeal joints.
There are nineteen individual muscles in the foot and lower leg that interconnect to help move the foot. Simply put, when muscles are overstressed or otherwise abnormal, they can affect the biomechanics of the foot because they can pull tendons and bones out of place and irritate joints. Conversely, a bone defect can cause muscle injury. I will discuss damage to particular muscles of the foot in great detail in subsequent chapters. I will also describe-particularly in Chapters 11 and 12, which deal with athletic activities-how muscles in the leg can affect or be affected by the biomechanics of the feet during various types of physical activities.
Tendons attach muscles to bones. Actually they are extensions of muscles. They are tough whitish cords that are somewhat elastic and flexible. When a muscle has been stretched to its maximum potential, the force of the stretch is transferred to the tendon. The tendon itself may then become overstretched, and the result is tendonitis, or inflammation of the tendon.
Ligaments are thick, inelastic, but slightly flexible structures that support and surround the joints, holding bone to bone. When an ankle is twisted or a big toe is stubbed, the cause of the discomfort and swelling is usually a ligament that has been overstretched or slightly torn.
Cartilage is dense connective tissue that serves as a lining on the ends of bones where they meet to form joints. If you look at the end of a chicken drumstick, you will notice white gristle lining the bone. That white gristle is cartilage.
Cartilage provides smooth surfaces between bones. Without cartilage, your body would literally grind to a halt. Your joints would make a terrible racket when you moved as bone ground against bone. You would also be in severe pain from inflammation in the joints caused by the bones grinding together.
Two main arteries supply the feet with the necessary blood: the dorsalis pedis artery and the posterior tibial artery. These major arteries spread oxygenated blood via smaller arterioles to the many tissues of the feet. If the arterial system fails to supply the life-supporting oxygen contained in the red blood cells, serious problems could result.
Because the major foot arteries are the farthest from the heart of any in the human body, many circulatory problems will first manifest themselves in the feet. Two examples are arteriosclerosis (hardening of the arteries) and atherosclerosis (a buildup of plaque inside the arteries, leading to their subsequent blockage).
We all know that veins are the vessels that return used blood to the heart and lungs for regeneration-that is, to obtain a new supply of nutrients and oxygen-after the blood's supply of oxygen has been used to nourish the tissues of the body. Two sets of veins return blood from the lower extremities to the heart and lungs. The superficial veins, which run close to the surface of the skin and move spent (deoxygenated) blood from the feet to the heart and lungs, are the great saphenous-the longest vein in the body, running up the big-toe side of the foot and along the inside of the leg-and the small saphenous, which runs along the outside part of the foot and up the back of the leg. The deep veins, farther below the surface of the skin, are the anterior tibial and the posterior tibial. The position of the saphenous veins can be seen in Figure 1.3. Incidentally, it is the great saphenous vein that heart surgeons sometimes use in bypass surgery.
Then there are tiny auxiliary veins (venuoles), which are the opposite of the arterioles that deliver fresh blood to various more remote areas of the body. The venuoles pick up used blood from the nether reaches of the feet and deliver it to the larger veins for the journey up to the heart and lungs. Capillaries are the crossover links between the arterioles and the venuoles.
People with circulatory problems in their lower extremities often complain of swollen ankles, a condition that worsens after a long day on one's feet or after a lengthy airplane flight. The majority of such problems, including varicose veins, are related to poor venous (vein) function in the feet. Treatments do exist for such conditions, and they will be described in detail in Chapter 10.
Podiatrists, and other medical professionals who are on their toes, will examine the feet of their patients for any changes in skin color, texture, and temperature. Such changes can be tip-offs to certain circulatory problems that will be described in Chapter 10. But I will tell you now that it is unwise to make any diagnoses yourself. If one of your toes looks and feels funny, don't assume that this indicates serious cardiovascular disease and go into a panic. See your doctor at once for a more reliable opinion.
On Your Nerves
Nerves supply feeling and muscle control to particular parts of the body, the foot being one of them. It has four major nerves to provide you with many weird and wonderful sensations. These four nerves are the posterior tibial, the superficial peroneal, the deep peroneal, and the sural.
Nerve problems in the foot are commonly related to compression syndromes-that is, a nerve is being pinched or squeezed. For example, an improperly fitting shoe can put so much pressure on a nerve that the area around the nerve swells. This causes nerve entrapment, which in turn can lead to pain and numbness, and occasionally to a strange, seemingly unrelated discomfort that I call "enigmatic pain." Nerve disorders in other parts of the body-for example, sciatica-can also have manifestations in the feet. These and other nerve diseases that affect the lower extremities will be discussed in various chapters throughout the book.
Functions of the Foot
Now that we know the roles of the major components of the foot, before we proceed to the chapter on biomechanics, we ought to briefly examine the functions of the foot. It is important to know what the foot does in order to be able to understand why its proper range of motions is so vital in keeping you on an even keel when you are walking or running.
First, the mobile foot helps you adapt to certain ground surfaces. If you have trouble adapting to walking or running on hard, soft, wet, or dry surfaces, you may fall flat on your face. The foot functions much as the tires of a car do to assure a smooth, safe ride on various terrains.
Second, the foot is a rigid lever that propels the body forward-and in other directions. Without this function you would have great difficulty maneuvering your body in any direction.
Excerpted from The Good Foot Book by Glenn Copeland Stanley Solomon Copyright © 2005 by Dr. Glenn Copeland and Stanley Solomon Enterprises Inc.. Excerpted by permission.
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