The most important congenital foot disorder is clubfoot, or talipes equinovarus, in which the foot is twisted inward and
downward through shortening of ligaments and tendons. In some
cases the condition is inherited, whereas in others it appears to be caused by diseases or other factors. Milder cases may be treated with a progressive series of casts, but more severe ones require surgery.
Other important congenital deformities involve the arch of the foot: flatfoot, or pes planus; and a narrow, rigid foot with a high arch, called pes cavus. Both cause pain, and both are usually treatable with arch supports. Surgery is required in some cases, however. One form of flatfoot, called pronation, is observed in infants and children and is usually not painful at that age. Ligament laxity allows the heels to roll outward, causing walking deformities and possible painfulness in later life unless corrected.
A bunion, or hallux valgus, is most commonly a disorder affecting the joint between the big toe and its metatarsal bone. The bursa, a fluid-filled sac in the joint, becomes inflamed and swells, causing pain and often twisting the big toe toward the second toe. The result is deformity and pain. Disabling bunions require surgery. Some cases are congenital, but most result from poorly fitting shoes. Corns are simply
skin thickenings that become painful as they taper into the skin and cause pressure on nerve endings.
Distinctive Conditions
Three skin disorders that can also affect other parts of the body have distinct features when they occur on the foot. One, the plantar wart (also called a verruca), is caused by the same virus as that of the common wart elsewhere. On the sole of the foot, however, the firm wart acts like a pebble in a shoe, pushing against deeper skin layers that give way before it and causing great pain. Plantar warts may be treated by such techniques as freezing.
Ingrown toenail involves common bacterial infection but in a specialized site. It occurs on the rim of the nail of the big toe, where shoe pressure causes the flap of skin to be forced over the nail. This carries bacteria beneath the skin surface, and infection results. Surgical removal of part of the nail may be required in severe cases.
A special variety of fungus disease, called athlete's foot, tinea pedis, is caused by Trichophyton nentagrophytes, T. rubrum, and other fungus species. Most commonly, it occurs when the moist warmth of socks acts as an incubator for fungi picked up from the environment.
General Disorders
Joints of the foot may be affected by the various forms of arthritis found elsewhere in the body. These include rheumatoid arthritis, osteoarthritis, and gout. The most common site for an attack of gout is the joint between the big toe and its metatarsal, as in bunions. Treatment of arthritis in the foot is substantially the same as in other parts of the body. Arthritic spurs on the big-toe joint cause rigidity that may make normal walking impossible in severe cases. Sometimes special shoes may be sufficient to alleviate the problem, but in some cases replacement of the joint with a synthetic one is required. Arthritic spurs are most common either on the top of the foot at the joint between the metatarsal and one of the ankle bones or on the heel bone. Such spurs may require surgical removal.
Inflammations of the back part of the foot are common. The one most frequently seen is tendonitis of the Achilles tendon, the large tendon of the back of the heel. The inflammation may be a symptom of gout but is more commonly the result of stress. The posterior tibial tendon, which runs along the inner side of the foot, is a similar cause of pain in persons with flatfoot. The plantar fascia, a thick sheet of fibrous tissue running from the heel bone forward to the joints between the metatarsals and the toes, is a major support of the long arch of the foot, and when it becomes inflamed it can cause great disability. Pain is usually releved by firm arch supports.
Arterial diseases not uncommonly affect the foot, particularly atherosclerosis. The disease is much more severe in the leg than in the arm, perhaps because of greater hydrostatic pressure. When artery narrowing caused by the disease is severe, the cells farthest from the heart receive insufficient oxygen and nutrients. Diseases of the arteries anywhere in the leg are likely to be observed first in the foot and especially in the toes, and they may produce extensive gangrene, or tissue death. Persons with diabetes may develop this condition, sometimes necessitating amputation of part or all of the lower extremity.
Injuries
The foot is prone to injury. Twisting of the foot relative to the lower leg results in fractures about the ankle. Toes and metatarsal bones may be crushed by falling objects, and jolts caused by jumping or other actions can fracture the heel bone. Hairline fractures of the second metatarsal bone, once called "march fractures" because they were observed in army recruits after a long march, are now frequently seen in joggers. They cause much pain and are hard to diagnose.