"Trench foot " is a medical condition caused by prolonged exposure of the feet to damp, unsanitary, and cold conditions. The use of the word "trench" in the name of this condition is a reference to trench warfare, mainly associated with World War I. Affected feet may become numb, affected by erythrosis (turning red) or cyanosis (turning blue) as a result of poor vascular supply, and feet may begin to have a decaying odour due to the possibility of the early stages of necrosis setting in. As the condition worsens, feet may also begin to swell. Advanced trench foot often involves blisters and open sores, which lead to fungal infections; this is sometimes called tropical ulcer (jungle rot).

If left untreated, trench foot usually results in gangrene, which can cause the need for amputation. If trench foot is treated properly, complete recovery is normal, though it is marked by severe short-term pain when feeling returns. As with other cold-related injuries, trench foot leaves sufferers more susceptible to it in the future.

Affected feet may become numb, by erythema (turning red) or cyanosis (turning blue) as a result of poor blood supply, and may begin emanating a decaying odor if the early stages of necrosis (tissue death) set in. As the condition worsens, feet may also begin to swell. Advanced trench foot often involves blisters and open sores, which lead to fungal infections; this is sometimes called tropical ulcer (jungle rot). If left untreated, trench foot usually results in gangrene, which may require amputation. If trench foot is treated properly, complete recovery is normal, though it is marked by severe short-term pain when feeling returns.

Immersion foot syndromes are a class of foot injury caused by water absorption in the outer layer of skin. There are different subclass names for this condition based on the temperature of the water to which the foot is exposed. These include trench foot, tropical immersion foot, and warm water immersion foot. In one 3-day military study, it was found that submersion in water allowing for a higher skin temperature resulted in worse skin maceration and pain.

Trench foot is a medical condition caused by prolonged exposure of the feet to damp, unsanitary, and cold conditions. It is one of many immersion foot syndromes. The use of the word "trench" in the name of this condition is a reference to trench warfare, mainly associated with World War I, which started in 1914.

Athlete's foot is divided into four categories or presentations: chronic interdigital athlete's foot, plantar (chronic scaly) athlete's foot (aka "moccasin foot"), acute ulcerative tinea pedis, and vesiculobullous athlete's foot. "Interdigital" means between the toes. "Plantar" here refers to the sole of the foot. The ulcerative condition includes macerated lesions with scaly borders. Maceration is the softening and breaking down of skin due to extensive exposure to moisture. A vesiculobullous disease is a type of mucocutaneous disease characterized by vesicles and bullae (blisters). Both vesicles and bullae are fluid-filled lesions, and they are distinguished by size (vesicles being less than 5–10 mm and bulla being larger than 5–10 mm, depending upon what definition is used).

Athlete's foot occurs most often between the toes (interdigital), with the space between the fourth and fifth digits most commonly afflicted. Cases of interdigital athlete's foot caused by "Trichophyton rubrum" may be symptomless, it may itch, or the skin between the toes may appear red or ulcerative (scaly, flaky, with soft and white if skin has been kept wet), with or without itching. An acute ulcerative variant of interdigital athlete's foot caused by "T. mentagrophytes" is characterized by pain, maceration of the skin, erosions and fissuring of the skin, crusting, and an odor due to secondary bacterial infection.

Plantar athlete's foot (moccasin foot) is also caused by "T. rubrum" which typically causes asymptomatic, slightly erythematous plaques (areas of redness of the skin) to form on the plantar surface (sole) of the foot that are often covered by fine, powdery hyperkeratotic scales.

The vesiculobullous type of athlete's foot is less common and is usually caused by "T. mentagrophytes" and is characterized by a sudden outbreak of itchy blisters and vesicles on an erythematous base, usually appearing on the sole of the foot. This subtype of athlete's foot is often complicated by secondary bacterial infection by "Streptococcus pyogenes" or "Staphylococcus aureus".

Athlete's foot, known medically as tinea pedis, is a common skin infection of the feet caused by fungus. Signs and symptoms often include itching, scaling, and redness. In severe cases the skin may blister. Athlete's foot fungus may infect any part of the foot, but most often grows between the toes. The next most common area is the bottom of the foot. The same fungus may also affect the nails or the hands. It is a member of the group of diseases known as tinea.

Athlete's foot is caused by a number of different fungi. These include species of "Trichophyton", "Epidermophyton", and "Microsporum". The condition is typically acquired by coming into contact with infected skin, or fungus in the environment. Common places where the fungi can survive are around swimming pools and in locker rooms. They may also be spread from other animals. Usually diagnosis is made based on signs and symptoms; however, it can be confirmed either by culture or seeing hyphae using a microscope.

Some methods of prevention include avoiding walking barefoot in public showers, keeping the toenails short, wearing big enough shoes, and changing socks daily. When infected, the feet should be kept dry and clean and wearing sandals may help. Treatment can be either with antifungal medication applied to the skin such as clotrimazole or for persistent infections antifungal medication that are taken by mouth such as terbinafine. The use of the cream is typically recommended for four weeks.

Athlete's foot was first medically described in 1908. Globally, athlete's foot affects about 15% of the population. Males are more often affected than females. It occurs most frequently in older children or younger adults. Historically it is believed to have been a rare condition, that became more frequent in the 1900s due to the great use of shoes, health clubs, war, and travel.

The first sign of a foot-rot infection is when the skin between the claws of the hoof begins to swell (cellulitis). Swelling usually appears 24 hours after infection. The skin between the toes may be very red and tender and the toes may separate because of all the swelling. This is very painful to the animal and can cause lameness. The animal may also have a raised body temperature. A crack can develop along the infected part and is yellow in color. The foot will have a foul odor. Tendons and joints in the area can become infected, which is much harder to treat. A condition known as "super foot rot" is seen in some animals. Super foot rot infection occurs much faster and is usually much more severe. Most normal foot rot treatments will not cure this foot rot and a veterinarian should be contacted immediately.

Vaccines have been developed, but their efficacy is questionable and the immunity they provide is of short duration.

Foot rot, or infectious pododermatitis, is a hoof infection commonly found in sheep, goats, and cattle. As the name suggests, it rots away the foot of the animal, more specifically the area between the two toes of the affected animal. It is extremely painful and contagious. It can be treated with a series of medications, but if not treated, the whole herd can become infected. The cause of the infection in cattle is two species of anaerobic bacteria, "Fusobacterium necrophorum" and "Bacteroides melaninogenicus". Both bacteria are common to the environment in which cattle live, and "Fusobacterium" is present in the rumen and fecal matter of the cattle. In sheep, "F. necrophorum" first invades the interdigital skin following damage to the skin, and causes interdigital lesions and slight inflammation. The second stage of the disease is marked by the invasion of the foot by the foot rot bacterium "Dichelobacter nodosus", a Gram-negative anaerobe. Usually, an injury to the skin between the hooves allows the bacteria to infect the animal. Another cause of foot rot may be high temperatures or humidity, causing the skin between the hooves to crack and let the bacteria infect the foot. This is one of the reasons foot rot is such a major problem in the summer. Foot rot is easily identifiable by its appearance and foul odor. Treatment is usually with an antibiotic medication, and preventing injury to the feet is the best way to prevent foot rot.

The disease is different in cattle and sheep and cross-infection is not thought to occur.

Often there is a distinction made between conditions of the dorsal skin and plantar skin. Common examples include callus thickened skin, fungal infections of the skin (athlete's foot) or nails (onychomycosis), viral infection of verrucae, and ingrowing toenails that may cause bacterial nail infections (paronychia).

Corns and calluses are chunky tough layers of skin that develop on the foot to protect underlying skin from pressure and friction. Corns and calluses are very common and do not look pleasant. Corns and calluses generally need treatment only if they cause problems. For most people, the best treatment of corns and calluses is to eliminate the source of friction or pressure.

Ingrown toe nail is a disorder where the nail starts to grow into the soft fleshy area of the toe. It causes intense redness, pain and swelling. Ingrown toe nails often affect the big toe. The best treatment for ingrown toe nails is to get the nail partially or completely removed.

Diseases of the foot generally are not limited, that is they are related to or manifest elsewhere in the body. However, the foot is often the first place some of these diseases or a sign or symptom of others appear. This is because of the foot's distance from the central circulation, the heart and its constant exposure to pressures from the ground and the weight of the body.

The foot may look simple but is a complex structure with 26 bones, 33 joints, numerous muscles, nerves and different ligament types. Any part of the foot can be affected. Some foot disorders may present with just a mild ache, but other foot disorders can be very serious and limit ability to walk or bear weight. Most minor cases of foot pain respond to home care treatments except when severe pain is present as it is a disabling condition and usually needs some type of medical attention. If foot pain is not treated in time, it can lead to long term disability and continuing damage to the foot.

Diabetic foot ulcer is a complication of diabetes. Diabetic foot ulcers are classified as either neuropathic, neuroischaemic or ischaemic.

Assessment of diabetic foot ulcer includes identifying risk factors such as diabetic peripheral neuropathy, noting that 50 percent of people are asymptomatic, and ruling out other causes of peripheral neuropathy such as alcohol abuse and spinal injury.

The location of the ulcer, its size, shape, depth and whether the tissue is granulating or sloughy needs to be considered. Further considerations include whether the there is malodour, condition of the border of the wound and palpable bone and sinus formation should be investigated. Signs of infection require to be considered such as development of grey or yellow tissue, purulent discharge, unpleasant smell, sinus, undermined edges and exposure of bone or tendon.

Identification of diabetic foot in medical databases, such as commercial claims and prescription data, is complicated by the lack of a specific ICD-9 code for diabetic foot and variation in coding practices. The following codes indicate ulcer of the lower limb or foot:

- 707.1 Ulcer of lower limbs, except pressure ulcer

- 707.14 Ulcer of heel and midfoot

- 707.15 Ulcer of other part of foot

- 707.19 Ulcer of other part of lower limb

One or more codes, in combination with a current or prior diagnosis of diabetes may be sufficient to conclude diabetic foot:

- 250.0 Diabetes Mellitus

- 250.8 Diabetes with other specified manifestations

A diabetic foot is a foot that exhibits any pathology that results directly from diabetes mellitus or any long-term (or "chronic") complication of diabetes mellitus. Presence of several characteristic diabetic foot pathologies such as infection, diabetic foot ulcer and neuropathic osteoarthropathy is called diabetic foot syndrome.

Due to the peripheral nerve dysfunction associated with diabetes (diabetic neuropathy), patients have a reduced ability to feel pain. This means that minor injuries may remain undiscovered for a long while. People with diabetes are also at risk of developing a diabetic foot ulcer. Research estimates that the lifetime incidence of foot ulcers within the diabetic community is around 15% and may become as high as 25%.

In diabetes, peripheral nerve dysfunction can be combined with peripheral artery disease (PAD) causing poor blood circulation to the extremities (diabetic angiopathy). Around half of patients with a diabetic foot ulcer have co-existing PAD.

Where wounds take a long time to heal, infection may set in and lower limb amputation may be necessary. Foot infection is the most common cause of non-traumatic amputation in people with diabetes.

Juvenile plantar dermatosis (also known as "Atopic winter feet," "Dermatitis plantaris sicca," "Forefoot dermatitis," "Moon-boot foot syndrome," and "Sweaty sock dermatitis") is a condition usually seen in children between the ages of 3 and 14, and involves the cracking and peeling of weight bearing areas of the soles of the feet. One of the earliest descriptions was made by British dermatologist Darrell Wilkinson.

Scaly foot causes lesions of the skin with dermatitis and thickening of the skin.

Commonly known as scaly face, scaly legs, or tassel foot, knemidocoptiasis affects primarily the face and legs of birds around the world worldwide and can be fatal.

Scaly foot, or knemidocoptiasis is a bird ailment that is common among caged birds and also affects many other bird species. It is caused by mites in the genus "Knemidocoptes" which burrow into the bird's flesh. The tunnels made by the mites within the skin cause dermatitis and scaly lesions. Scaly face is caused by the same mite responsible for scaly foot and other related mites cause depluming. The condition is transmitted from one bird to another by direct prolonged contact.

Yoga foot drop is a kind of drop foot, a gait abnormality. It is caused by a prolonged sitting on heels, a common yoga position of vajrasana. The name was suggested by Joseph Chusid, MD, in 1971, who reported a case of foot drop in a student who complained about increasing difficulty to walk, run, or climb stairs. The cause was thought to be injury to the common peroneal nerve, which is compressed and thereby deprived of blood flow while kneeling.

Yoga foot drop is a potential adverse effect of yoga, allegedly unmentioned by yoga teachers and books.

Sufferers experience pain and swelling in the middle part of the foot and usually limp as a result. Patients that walk with a limp tend to walk with increased weight on the lateral side of the foot. Also, there can be tenderness over the navicular. Patients often complain of pain over the apex.

An X-ray of both feet is used to diagnose disease. The affected foot tends to have a sclerotic and flattened navicular bone.

The symptoms can occur anywhere between days to months after administration of the offending medication, depending on the dose and speed of administration (Baack and Burgdorf, 1991; Demirçay, 1997). The patient first experiences tingling and/or numbness of the palms and soles that evolves into painful, symmetric, and well-demarcated swelling and red plaques. This is followed by peeling of the skin and resolution of the symptoms (Apisarnthanarax and Duvic 2003).

Many medical professionals can diagnose a flat foot by examining the patient standing or just looking at them. On going up onto tip toe the deformity will correct when this is a flexible flat foot in a child with lax joints. Such correction is not seen in adults with a rigid flat foot.

An easy and traditional home diagnosis is the "wet footprint" test, performed by wetting the feet in water and then standing on a smooth, level surface such as smooth concrete or thin cardboard or heavy paper. Usually, the more the sole of the foot that makes contact (leaves a footprint), the flatter the foot. In more extreme cases, known as a kinked flatfoot, the entire inner edge of the footprint may actually bulge outward, where in a normal to high arch this part of the sole of the foot does not make contact with the ground at all.

On plain radiography, flat feet can be diagnosed and graded by several measures, the most important being the talonavicular coverage angle, the calcaneal pitch, and the talar-1st metatarsal angle (Meary's angle). The talonavicular coverage angle is abnormally laterally rotated in flat feet. It is normally up to 7 degrees laterally rotated, so a greater rotation indicates flat feet.

As with certain cases of flat feet, high arches may be painful due to metatarsal compression; however, high arches— particularly if they are flexible or properly cared-for—may be an asymptomatic condition.

People with pes cavus sometimes—though not always—have difficulty finding shoes that fit and may require support in their shoes. Children with high arches who have difficulty walking may wear specially-designed insoles, which are available in various sizes and can be made to order.

Individuals with pes cavus frequently report foot pain, which can lead to a significant limitation in function. The range of complaints reported in the literature include metatarsalgia, pain under the first metatarsal, plantar fasciitis, painful callosities, ankle arthritis, and Achilles tendonitis.

There are many other symptoms believed to be related to the cavus foot. These include shoe-fitting problems, lateral ankle instability, lower limb stress fractures, knee pain, iliotibial band friction syndrome, back pain and tripping.

Foot pain in people with pes cavus may result from abnormal plantar pressure loading because, structurally, the cavoid foot is regarded as being rigid and non-shock absorbent and having reduced ground contact area. There have previously been reports of an association between excessive plantar pressure and foot pathology in people with pes cavus.

Flat feet (also called pes planus or fallen arches) is a postural deformity in which the arches of the foot collapse, with the entire sole of the foot coming into complete or near-complete contact with the ground. Some individuals (an estimated 20–30% of the general population) have an arch that simply never develops in one foot (unilaterally) or both feet (bilaterally).

There is a functional relationship between the structure of the arch of the foot and the biomechanics of the lower leg. The arch provides an elastic, springy connection between the forefoot and the hind foot. This association safeguards so that a majority of the forces incurred during weight bearing of the foot can be dissipated before the force reaches the long bones of the leg and thigh.

In pes planus, the head of the talus bone is displaced medially and distal from the navicular. As a result, the Plantar calcaneonavicular ligament (spring ligament) and the tendon of the tibialis posterior muscle are stretched, so much so that the individual with pes planus loses the function of the medial longitudinal arch (MLA). If the MLA is absent or nonfunctional in both the seated and standing positions, the individual has “rigid” flatfoot. If the MLA is present and functional while the individual is sitting or standing up on their toes, but this arch disappears when assuming a foot-flat stance, the individual has “supple” flatfoot. This latter condition can be correctable with well-fitting arch supports.

Three studies (see citations below in military section) of military recruits have shown no evidence of later increased injury, or foot problems, due to flat feet, in a population of people who reach military service age without prior foot problems. However, these studies cannot be used to judge possible future damage from this condition when diagnosed at younger ages. They also cannot be applied to persons whose flat feet are associated with foot symptoms, or certain symptoms in other parts of the body (such as the leg or back) possibly referable to the foot.

On weightbearing projectional radiography, pes cavus can be diagnosed and graded by several features, the most important being medial peritalar subluxation, increased calcaneal pitch (variable) and abnormal "talar-1st metatarsal angle" (Meary's angle). Medial peritalar subluxation can be demonstrated by a medially rotated talonavicular coverage angle.

Rocker bottom foot, also known as congenital vertical talus, is an anomaly of the foot. It is characterized by a prominent calcaneus (heel bone) and a convex rounded bottom of the foot. It gets its name from the foot's resemblance to the bottom of a rocking chair.

It can be associated with Edwards' syndrome (trisomy 18), Patau syndrome (trisomy 13), Trisomy 9 and mutation in the gene HOXD10.

It can also be associated with Charcots foot.

Chemotherapy-induced acral erythema (also known as palmar-plantar erythrodysesthesia, palmoplantar erythrodysesthesia, or hand-foot syndrome) is reddening, swelling, numbness and desquamation (skin sloughing or peeling) on palms of the hands and soles of the feet (and, occasionally, on the knees, elbows, and elsewhere) that can occur after chemotherapy in patients with cancer. Hand-foot syndrome is also rarely seen in sickle-cell disease. These skin changes usually are well demarcated. Acral erythema typically disappears within a few weeks after discontinuation of the offending drug.