The Foot

The foot is a complex structure of 26 bones and 33 joints layered with an intertwining web of 126 muscles, ligaments, and nerves. The average person spends four hours on their feet and takes between 8,000 and 10,000 steps each day. The feet are very small relative to the rest of the body, and the impact of every step exerts tremendous force upon them -- about 50% greater than the person's body weight. During an average day the feet support a combined force equivalent to several hundred tons. In addition to supporting weight, the foot acts as a shock absorber and as a lever to propel the leg forward, and it serves to balance and adjusts the body to uneven surfaces. It is not surprising, then, that about 75% of Americans experience foot pain at some point in their lives. According to a recent study, chronic and severe foot pain is a serious burden for one in seven older disabled women. To compound problems, the lower back is often affected by injuries or abnormalities in the feet.

What Is Foot Pain?

Foot pain is generally defined by one of three sites of origin: the toes; the front of the foot (forefoot); or back of the foot (hind foot). Toe problems most often occur because of the pressure imposed by ill-fitting shoes. Pain originating in the front of the foot usually involves the metatarsal bones (five long bones that extend from the front of the arch to the bones in the toe) and the sesamoid bones (two small bones imbedded at the top of the first metatarsal bone, which connects to the big toe). Pain originating in the back of the foot can affect parts of the foot extending from the heel, across the sole (known as the plantar) to the ball of the foot.

General Conditions Causing Foot Pain

The causes of most incidents of foot pain are poorly fitting shoes. High-heeled shoes are major culprits for aggravating, if not causing, problems in the toes, where the most pressure is exerted. Other conditions can also cause or exacerbate foot pain. Weather affects the feet; they contract in cold and expand in hot weather. Foot size can also increase by 5% over the day and change shape and size depending on whether a person is walking, sitting, or standing. Improper walking due to poor posture or inherited or medical conditions that cause imbalance or poor circulation can contribute to foot pain. Often one leg is shorter than the other, causing an imbalance. High impact exercising, such as jogging or strenuous aerobics, can injure the feet. Common injuries include corns, calluses, blisters, muscle cramps, acute knee and ankle injuries, plantar fasciitis, and metatarsalgia.

Medical Conditions Causing Foot Pain

Arthritic conditions, particularly osteoarthritis and gout, can cause foot pain. Although rheumatoid arthritis almost always develops in the hand, the ball of the foot can also be affected. Osteoporosis, in which bone loss occurs, can also cause foot pain. Diabetes is a particularly serious cause of foot pain, infection, and ulcers, and, without proper foot care, can result in amputation. Diabetics with foot deformities, such as claw toes, or bunions are at particular risk. Anorexia, high blood pressure, and other diseases that affect the nervous and circulatory systems can cause pain, loss of sensation, and tingling in the feet, as well as increase the susceptibility for infection and foot ulcers. A number of conditions, including pregnancy, heart failure, kidney disease, and hypothyroidism, can cause fluid build-up and swollen feet. The increased weight and imbalance of pregnancy contributes to foot stress. Diseases that affect muscle and motor control, such as Parkinson's disease, also cause foot problems. Some medications, such as calcitonin and drugs used for high blood pressure, can cause foot swelling.

Causes of Toe Pain

• Corns

  A corn is actually a form of a callus -- a protective layer of dead skin cells composed of a tough protein called keratin. A corn itself is cone-shaped and usually develops if a shoe rubs against the toes for a prolonged period. As the skin thickens, the corn forms a knobby core that points inward. Hard corns develop on toe joints, usually on the little toe. A shoe that squeezes the front of the foot may cause one toe to rub against another forming a corn between the toes, which is usually soft. These corns can be painful, however, if they harden and rub against each other.

• Ingrown Toenails.

  Ingrown toenails can occur in any toe but are most common in the big toes. They usually develop when tight fitting or narrow shoes put too much pressure on the toenail and force the nail to grow down into the flesh of the toe. Incorrect toenail trimming can also contribute to the risk of developing an ingrown toenail (see How Is Foot Pain Prevented, in this report). Fungal infections, injuries, abnormalities in the structure of the foot, and repeated pressure to the toenail from high impact aerobic exercise can also produce ingrown toenails.

• Bunions

  A bunion is a deformity that usually occurs at the head of the first of five long bones (the metatarsal bones) that extend from the arch and connect to the toes. The first metatarsal bone is the one that attaches to the big toe. The big toe is forced in toward the rest of the toes, causing the head of the first metatarsal bone to jut out and rub against the side of the shoe; the underlying tissue becomes inflamed and a painful bump forms. As this bony growth develops, the bunion is formed as the big toe is forced to grow at an increasing angle towards the rest of the toes. A bunion may also develop in the bone that joins the little toe to the foot (the fifth metatarsal bone), in which case it is known as a bunionette or tailor's bunion.

  Bunions often develop from wearing narrow, high-heeled shoes with pointed toes, which puts enormous pressure on the front of the foot and causes the foot and toes to rest at unnatural angles. Injury in the joint may also cause a bunion to develop over time. Genetics play a factor in 10% to 15% of all bunion problems; one inherited deformity, hallux valgus, causes the bone and joint of the big toe to shift and grow inward, so that the second toe crosses over it. Flat feet, gout, and arthritis increase the risk for bunions.

• Hammertoes

  A hammertoe is a permanent deformity of the toe joint in which the toe bends up slightly and then curls downward, resting on its tip; when forced into this position long enough, the tendons of the toe contract and it stiffens into a hammer- or claw-like shape. Hammertoe is most common in the second toe but may develop in any or all of the three middle toes if they are pushed forward and do not have enough room to lie flat in the shoe. The risk is increased when the toes are already crowded by the pressure of a bunion. Lying down for long periods, diabetes, and various diseases that affect the nerves and muscles put people at risk.

Causes of Pain in the Front of the Foot

The incidence of forefoot pain and deformity increases with age. With early diagnosis, conservative therapy is often successful in treating common disorders of the forefoot.

• Calluses

  Calluses are composed of the same material as corns -- hardened patches of dead skin cells formed from keratin -- but calluses develop on the ball or heel of the foot. The skin on the sole of the foot is ordinarily about forty times thicker than skin anywhere else on the body, but a callus can double this normal thickness. A protective callus layer naturally develops to guard against excessive pressure and chafing as people get older and the padding of fat on the bottom of the foot thins out. If calluses get too big or too hard, however, they may pull and tear the underlying skin. Calluses can develop from wearing poorly fitting shoes and walking on hard surfaces. People with flat feet are at an increased risk of developing calluses. In people with diabetes, particularly those who have had foot ulcers, the presence of calluses is a strong predictor of subsequent ulceration.

• Neuromas

  Neuromas occur when the tissue surrounding a nerve becomes enlarged and inflamed causing a burning or tingling sensation and cramping. Morton's neuroma is the most common neuroma in the foot and usually develops when tight, poorly fitting shoes, often those with high-heels, cause the third and fourth metatarsal bones to pinch together compressing an underlying nerve. Injury, arthritis, or abnormal bone structures may also cause this condition.

• Stress Fracture

  A stress fracture in the foot, also called fatigue or march fracture, usually occurs from a break or rupture in any of the five metatarsal bones (mostly in the second or third). Fracture in the first metatarsal bone that leads to the big toe is uncommon because of the thickness of this bone. If it occurs there, it is more serious than fractures in the other metatarsal bones, because it dramatically changes the pattern of normal walking and weight bearing. (Stress fractures can also occur in the heel area.) They are caused by overuse during strenuous exercise, particularly jogging and high-impact aerobics.

• Sesamoiditis

  Sesamoiditis is an inflammation of the tendons around the small, round bones that are imbedded in the head of the first metatarsal bone, which leads to the big toe. Sesamoid bones bear much stress under ordinary circumstances; excessive stress can strain the surrounding tendons. Often there is no clear-cut cause, but sesamoid injuries are common among people who participate in jarring, high impact activities, such as ballet dancing, jogging, and aerobic exercise.

• Metatarsalgia

  When a cause cannot be determined, any pain on the bottom of the foot where the metatarsal bones connect to the four lesser toes is generally referred to as metatarsalgia.

Causes of Pain in the Heel and Back of the Foot

The heel is the largest bone in the foot. Heel pain is the most common foot problem and affects two million Americans every year. It can occur in the front, back, or bottom of the heel.

• Plantar Fasciitis

  Plantar fasciitis occurs from small tears and inflammation in the wide band of tendons and ligaments -- the connective tissue -- which stretches from the heel to the ball of the foot. This band, much like the tensed string in a bow, forms the arch of the foot and helps to serve as a shock absorber for the body. (The term plantar means the sole of the foot and fascia refers to any fibrous connective tissue in the body.) Plantar fasciitis is usually a result of overuse from high-impact exercise and sports and accounts for up to 9% of all running injuries. Because the condition often occurs in only one foot, however, factors other than overuse may be responsible in some cases. Other causes of this injury include poorly fitting shoes or an uneven stride that causes an abnormal and stressful impact on the foot. Pain often occurs suddenly and mainly in the heel. The condition can be temporary or may become chronic if the problem is ignored. In such cases, resting provides relief, but it is only temporary.

• Bursitis of the Heel

  Bursitis of the heel is an inflammation of the bursa, a small sack of fluid tissue, beneath the heel bone.

• Haglund's Deformity

  Haglund's deformity (also commonly called pump bump and known medically as posterior calcaneal exostosis) is a bony growth surrounded by tender tissue on the back of the heel bone. It develops when the back of the shoe, almost always one with a high heel, repeatedly rubs against the back of the heel, aggravating the tissue and the underlying bone.

• Tarsal Tunnel Syndrome

  Tarsal tunnel syndrome results from compression to a nerve that runs through a narrow passage behind the inner ankle bone down to the heel. It is caused by injury to the ankle, such as a sprain or fracture, or by a growth that presses against the nerve.

• Achilles Tendinitis

  Achilles tendinitis is an inflammation of the tendon that connects the calf muscles to the heel bone. Achilles tendinitis is caused by small tears in the tendon from overuse or injury. It is most common in people who engage in high-impact exercise, particularly jogging, racquetball, and tennis. People at highest risk for this disorder are those with a shortened Achilles tendon, which can be due to an inborn structural abnormality or can be acquired after wearing high heels regularly. Such people tend to roll their feet too far inward when walking and bounce when they walk.

• Heel Spurs

  Heel spurs are calcium deposits that develop over time into a sharp bony growth under the heel bone. They often result from improper foot movement during running or walking, poorly fitting shoes, and excessive body weight. As a spur develops the soft tissue in the heel becomes irritated and swells, putting pressure on the nerves and causing pain. Pain may increase with age as the fatty tissue on the bottom of the foot wears away. It should be noted, however, that plantar fascia, bursitis, stress fractures, and tarsal tunnel syndrome are more likely to be the cause of heel pain than spurs.

• Excessive Pronation

  Pronation is the normal motion that allows the foot to adapt to uneven walking surfaces and to absorb shock. Excessive pronation occurs when the foot has a tendency to turn inwardly and stretch and pull the fascia. It can cause not only heel pain, but hip, knee, and lower back problems.

Causes of Arch and Bottom-of-the-Foot Pain

• Flat Foot

  Flatfoot, or pes planus, is a defect of the foot, in which there is no arch at all. Flatfoot is usually hereditary or caused by diseases of the muscles and nerves. Arches can fall, however, under certain conditions. At particular risk are women who have habitually worn high-heels for long periods. In such cases, the Achilles tendon that runs down the back of the calf to the heel bone is not stretched, so over the years, it shortens and tightens. The ankle, then, does not bend properly, and tendons and ligaments running through the arch try to compensate. Sometimes, they then break down and the arch falls. Some studies have indicated that the earlier one starts wearing shoes, particularly for long periods of the day, the higher the risk for flat feet. One indirect outcome of flat arches may be urinary incontinence or leakage during exercise. The less flexible the arch, the more force reaches the pelvic floor, jarring the muscles that affect urinary continence.

• Clawfoot and Abnormally High Arches

  Clawfoot, or pes cavus, is a deformity of the foot marked by very high arches and very long toes. Clawfoot is a hereditary condition, but it can also occur when muscles in the foot contract or become unbalanced due to nerve or muscle disorders. An overly high arch (hollow foot), in general, can cause problems. Army studies have found that recruits with the highest arches have the most lower-limb injuries and that flat-footed recruits have the least. Contrary to the general impression, the hollow foot is much more common than the flat foot.