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The feet are the foundation of our bodies, and they assist us in some of the most basic functions of living. Each foot contains 26 bones, which are controlled by multiple ligaments, muscles, and tendons.[1]
Through activities of living, the feet can change structurally over time, causing a reshaping of the feet. This can give rise to a number of medical conditions and deformities. In addition, the feet are susceptible to infections—including bacterial, fungal, and viral infections. Systemic illnesses can also affect and change the feet, which can limit daily activity and quality of life.
The image shows gangrene of the first to fourth toes of the right foot in a person with diabetes.
Image courtesy of Wikimedia Commons/James Heilman, MD.
In a normal foot, the gait cycle (walking) begins with the arch in a flattened position, allowing the foot to be loose enough to adapt to the terrain. When the leg is perpendicular to the ground, the arch begins to rise to allow the foot to lock and support the weight of the body as it is propelled forward. In individuals with a flat foot (pes planus), the foot stays loose and unlocked.
In those with a high arch (pes cavus), the arch does not flatten with weight bearing[2] and the foot stays locked—the foot is not flexible and thus pounds the ground as the person walks. Neurologic conditions, such as cerebral palsy and Charcot-Marie-Tooth (CMT), can result in a structurally high arched foot.[2]
Many patients with a pes cavus can develop calluses and pain at the heel and ball of the foot.[2] Treatment requires an accommodation to help absorb the increased pressures in these regions, such as different inserts to pad the foot rather than control its movement.
Image courtesy of Douglas A Albreski, DPM.
The opposite of a high arched foot is a flat foot (pes planus), which, due to its structure, is "loose." Flat foot is among the most common structural deformities of the foot, in which the medial arch is collapsed or begins to collapse at some point.[3] This deformity can be congenital or acquired if ligaments can no longer support the foot structure because they are injured (posterior tibial tendon dysfunction) or become mal-aligned later in life.
For a person with a congenital foot deformity of this nature, there are increased strains on ligaments and tendons, resulting in medial arch pain and overuse injuries (eg, tibial stress fractures).[4] Treatment requires providing support to the foot in order to control the motion of the foot. These supports may include supportive shoes, inserts, or prescription orthotic devices.[3,4] In severe cases, surgical interventions may also be necessary.
Images of flat feet courtesy of Douglas A Albreski, DPM.
Hammer toes (shown) and claw toes are also common foot deformities named for their appearance. In a normal lesser toe (toes not including the big toe), there are three phalanges connected by two joints.[5] When the joint closest to the foot, the proximal joint, contracts, it is referred to as a hammer toe.[5,6] If the joint closer to the nail, the distal joint, is contracted, the deformity is referred to as a claw toe.[6] In addition, there may be a rotation of the toe, referred to as an adducto varus deformity, which is commonly seen in the fourth and fifth toes.[7]
Early on in a toe deformity, discomfort from an ill-fitting shoe may result in redness and soreness to that area. Over time, this condition can worsen, resulting in calluses that may cause additional discomfort.[5] Initial treatments include shoe gear changes (such as those with a higher toe box), protective padding, and/or reduction of the callus to help accommodate the deformities.[5,6] If the initial therapy doesn't help and pain persists, surgical intervention may be required.
Hammer toes and claw toes can be flexible (the toes can be manually straightened) or rigid (the joints are fused and no longer function). A flexible deformity may require only soft-tissue correction, whereas a rigid deformity most likely requires bone reconstruction in order to straighten the toe and reduce the painful symptoms.[5,6]
Images courtesy of Medscape (left) and Douglas A Albreski, DPM (right).
When tendons and ligaments do not stabilize the great toe, the big toe can deviate and/or rotate, resulting in a prominent big toe joint (bunion) along the side of the foot.[8] With early detection and stabilization of the foot (supportive shoes, inserts, or prescription orthotic devices), symptoms may be prevented.
Mal-alignment of the great toe joint causes bony proliferation, resulting in development of the classic protrusion of the side of the big toe joint.[8] This may lead to swelling and increased pain, most commonly when a person wears tight and/or narrow shoes; these flares can be controlled through rest, icing, and proper shoe selection. If the flares worsen, medical attention may be required, utilizing anti-inflammatory medications.[8] If symptoms and pain become persistent, surgical intervention may be necessary; this may include reconstruction and stabilization of the great toe joint.
The radiograph demonstrates a severe bunion deformity.
Image courtesy of Medscape/Richard Laughlin, MD.
In hallux limitus, changes occur to the top of the great toe joint (metatarsophalangeal [MTP] joint) (rather than to the side, as seen in a bunion), limiting its ability to bend backward.[9] During normal walking and lifting of the heel off the ground, the great toe dorsiflexes and the MTP joint bends. If the great toe joint is compressed, there is a reduction in the range of motion (ROM), which results in increased pressure to the top of the joint.[10] Over time, osseous changes occur, which further reduces the ROM of the great toe joint. This process can continue and result in a fusion of the great toe joint (ie, stiff big toe or hallux rigidus).[9,10]
Symptoms initially include pain within the joint, associated with increased activity.[9,10] Due to the limited ROM, increased pressure along the side of the great toe can result in callus formation.
Conservative treatment includes using oral anti-inflammatory agents, wearing shoes with stiffer soles to reduce motion, and/or adding shoe inserts to artificially increase motion of the great toe joint.[9,10] If pain persists, surgical intervention may be necessary, ranging from reduction of the osseous growth to decompression of the great toe joint.[9,10] These procedures help to restore the ROM in the great toe joint to prevent symptoms.
The image demonstrates a simple test to evaluate for hallux limitus. MP = metatarsophalangeal; MP1 = first metatarsophalangeal; ROM = range of motion.
Image courtesy of Wikimedia Commons/Ctzioupis.
Ingrown nails (onychocryptosis, unguis incarnatus[11,12]) are most commonly seen in children and young adults, as well as in the older population.[11] In young patients, ingrown nails are usually due to inconsistent growth of the toe structures, resulting in the nail border penetrating the skin; later in life, ingrown nails are commonly seen when the bone structure changes, resulting in nail deformity.[13] Other causes include cutting a nail too short along the lateral portion, such that the nail fold is irritated or penetrated, as well as external compression from shoes that are too tight.[11-13]
Early signs/symptoms include pain and discomfort along the edge of the nail plate, usually affecting the end of the nail. As the nail irritates the skin, a callus can develop, causing persistent discomfort. If left untreated, the nail may penetrate the tissue and potentially result in an infection. Treatment generally involves conservative management in the early stages; later, advanced stages of ingrown toenails are generally managed by removal of the offending nail border and, if infection is seen, administering topical and/or oral antibiotics.[11-13]
Images courtesy of Medscape (left) and Douglas A Albreski, DPM (right).
Athlete's foot (tinea pedis) is a common cutaneous condition in which fungus infects the skin of the foot.[14] Acute and chronic forms of athlete's foot exist. In the acute condition, blister formation occurs on the arches of the feet; the blisters are usually filled with clear yellow fluid. However, the skin between the toes, or the web spaces, may also be affected, causing redness and peeling of the skin (bottom right).[14] Symptoms include pruritus or a burning sensation.
The chronic condition presents with a moccasin distribution (left, bottom center), in which the bottom of the foot is usually red and scaly.[14] Again, symptoms can include pruritus and burning, although it is not uncommon for a patient to be asymptomatic. This condition is often associated with fungal nail changes, in which the fungus within the nail continually reinfects the skin.
Treatments include topical prescription and/or over-the-counter (OTC) antifungal medications, which have a high success rate.[14] In severe cases, oral antifungals or topical corticosteroids may be necessary.
Images of tinea pedis in different patients courtesy of (1) Wikimedia Commons/James Heilman, MD (left, bottom center), (2) Douglas A Albreski, DPM (top right), and (3) Wikimedia Commons/Falloonb (bottom right).
Onychomycosis is a fungal infection of the nail that is caused by an interruption of the nail plate and nail bed, allowing the fungus to grow. This is commonly seen when an injury occurs to the nail, either from repetitive trauma through athletic activities or from direct trauma, such as dropping something heavy on a toe.[15] Common nail changes seen with onychomycosis include discoloration (yellow brown), thickening of the nail, separation of the nail from the nail bed, and debris underneath the nail.[15,16]
Although onychomycosis is a common nail condition, formal diagnosis is required, because there are multiple medical conditions that can mimic these changes. Workup includes direct microscopy, periodic acid–Schiff staining, culture, and histology.[16] Treatments include prescription and OTC topical antifungal medications. Oral antifungal medications offer higher success rates, but use of these medications requires medical monitoring.[16]
Image courtesy of Douglas A Albreski, DPM.
Verrucous skin growths on the plantar surface are caused by the human papillomavirus (HPV)[17] and have a few common characteristics, as follows[17,18]:
Calluses are commonly misdiagnosed as warts, but calluses generally appear near bony prominences, such as joints, have skin lines that go through them, and are more painful with direct pressure.[18]
Plantar verrucas are usually self-limiting and can resolve without treatment. However, there are countless treatment options, ranging from duct tape and surgery, to freezing, laser, and topical acids[18,19]; all of these are designed to irritate the wart, allowing the body to react to the irritant and recognize the viral infection. This condition is prevalent in children, in whom treatments have a high success rate. However, once patients are beyond the teenage years, treatment success rates are lower, and this condition may require medical and/or surgical intervention.
Images courtesy of Douglas A Albreski, DPM (left) and Wikimedia Commons/James Heilman, MD (right).
A subungual exostosis is a benign tumor composed of bone and cartilage that can grow out from the distal phalanx.[20,21] This growth, which usually occurs underneath the nail bed, can result in a deformity to the toe. The center of the nail may lift up, leading to a "pincher toenail." A more distal growth can push the nail bed out from beneath the nail, giving the appearance of a skin growth below the nail plate (left). When this occurs, it is commonly mistaken for a wart, and a radiographic examination of the toe is necessary to confirm the diagnosis (right).
The only treatment for the excessive bone growth, besides observation, is surgical removal of the lesion and curettage of the underlying bone.[20,21] Subungual exostoses are usually found in children and young adolescents, whose feet and toes are still growing.
Images courtesy of Douglas A Albreski, DPM.
Inflammatory skin conditions, including eczema, are referred to as spongiotic dermatitis, in which intercellular edema within the epidermis (spongiosis) leads to widening of the intercellular spaces between keratinocytes and elongation of the intercellular bridges, which may progress to intraepidermal vesiculation.[22] The inflammatory process evolves over time, causing the skin to become erythematous, scaly, and pruritic. In more severe cases, pustules may form.
Because there are many causes of spongiotic dermatitis, it is sometimes difficult to determine the exact etiology.[23] Most often, it results from a hypersensitivity reaction. The precipitating factor can be an external exposure, such as a contact allergen (eg, detergents, soaps, shoe material), or an internal exposure, such as those relating to food (food allergies) and medications. Other factors can include insect bites or a viral or bacterial infection.
The primary treatment is attempting to identify the cause and then removing the source of the inflammation.[24] This condition also requires topical corticosteroids to help decrease the inflammatory process. Due to the break in the skin's protective barrier, the risk of infection is present, potentially leading to secondary infections.[24] Therefore, the patient may require additional medical care or treatment.
Image courtesy of Douglas A Albreski, DPM.
Psoriasis is a common inflammatory skin condition that involves the formation of plaques and scales, most often affecting the elbows, knees, lumbosacral region, and/or scalp.[25] This condition can also affect the feet, often presenting as thickening and yellowing of the skin on the plantar surface (shown). Another form of psoriasis can cause pustules, which are sterile abscesses; these usually occur on the arch, side, or sole of the foot.
Symptoms of psoriasis may include chronic itch and burning pain.[25] When the sole is affected, the patient may experience more severe discomfort when standing or walking, which can become debilitating and impede ambulation.
Initial treatments depend on the severity of the psoriasis, but they typically involve topical corticosteroids or other topical anti-inflammatory medications.[25] In more severe cases, oral and injectable medications, including immunosuppressant and biologic agents, may be required.[25-28]
Image courtesy of Douglas A Albreski, DPM.
When psoriasis involves joints, it is known as psoriatic arthritis.[29,30] According to the 2016 Global Report on Psoriasis by the World Health Organization (WHO), between 1.3% and 34.7% of patients with psoriasis will develop psoriatic arthritis; in two large German studies, the prevalence of arthritis was approximately 20%.[29] Although rare, patients can experience psoriatic arthritis without, or with only minimal, skin involvement.[29]
The foot is commonly affected, with involvement of the distal joints of the lesser toes or the middle joint of the great toe.[30] This is can be a very destructive type of arthritis, in which periarticular erosions transform the normal ball-and-socket joint into a "pencil and cup," wherein the normal rounded ball of the distal head of a bone becomes shaped like a spike or point and the end of the neighboring bone appears to have a cup or saucer shape (right). As a result of this process, the affected toes swell and become tender (left). Changes to the nails may also occur, with a classic pitting appearance of the nail plate.[30]
Due to the destructive changes of this condition and to ensure joint preservation, treatment options are usually more aggressive than those for psoriasis alone, including the use of disease-modifying anti-rheumatic drugs (DMARDs), alone or in combination, and biologics such as anti-tumor necrosis factor (anti-TNF) agents.[30,31]
The left image demonstrates severe psoriatic arthritis in the feet of a patient. The right image shows extensive bony destruction around the interphalangeal joint of the second toe in a different patient. There is associated widening of the joint space, which helps distinguish this condition from osteoarthritis. The base of the middle phalanx is expanded, and there is diffuse soft-tissue swelling but no osteoporosis. Marked osseous erosion about the joint has produced a characteristic pencil-in-cup deformity.
Images courtesy of Wikimedia Commons/James Heilman, MD, (photograph), and Michael R Aiello, MD (radiograph).
Rheumatoid arthritis is another systemic inflammatory disease that affects multiple joints, particularly the lining of joints, but it also has the potential for extra-articular manifestations.[32,33] According to the Centers for Disease and Control and Prevention (CDC), the lifetime risk of rheumatoid arthritis appears to be approximately 4% for women and 3% for men.[33]
Signs/symptoms usually begin with pain and swelling that affect both feet.[32] As the condition progresses, the joints become affected. Arthritic changes can mal-align the joints and ultimately cause structural changes. As these changes develop, increased pressure is applied to the soft tissue, resulting in painful corns and calluses. In the rear foot, collapse of the arch can occur, resulting in further structural changes and difficulty in walking.[32] The foot may become so deformed that the patient is unable to wear a normal shoe. Custom molded shoes may be required to offload pressures on the foot in order to avoid painful ambulation.
Conservative therapy can include therapeutic exercises and reduction of painful corns and calluses. Pharmacologic management includes the use of nonbiologic and biologic DMARDs, immunosupppressants, and corticosteroids, alone or in combination.[32-34] In extreme cases, surgical reconstruction of the foot may be necessary.[32]
The lateral radiograph of a foot (left) shows destruction of the talonavicular joint with narrowing of the joint space. The photograph on the right shows rheumatoid changes and soft-tissue swelling in the foot of another patient.
Images courtesy of (1) Popelka S, Hromadka R, Vavrik P, et al. BMC Musculoskelet Disord. 2010;11:38. [Open access.] PMID: 20187969, PMCID: PMC2837861 (left); and (2) Douglas A Albreski, DPM (right).
According to 2014 CDC statistics, an estimated 9.3% of the US population (29.1 million people) have diabetes. Of these individuals, 21 million have been diagnosed, leaving an additional 8.1 million (27.8%) people who remain undiagnosed and who may be unaware of their condition.[35] In developed countries, diabetes is the leading cause for nontraumatic amputations of the lower extremities.[36,37]
Diabetes affects multiple organ systems and commonly causes foot problems in what is referred to as the diabetic foot triad of neuropathy, ischemia, and infection.[38] Elevated blood sugars impact the neurologic system and cause a loss of feeling in the lower extremities, which often results in the patient being unaware of an injury (eg, cuts, burns, sores, abrasions from an excessively tight shoe).[38,39] The problem is compounded by the diabetic patient's compromised vascular system, in which there is essentially an insufficient blood supply due to decreased circulation to effectively heal the injuries.[38,40] This situation is further complicated by the fact that a prolonged open sore can become infected.[38,40] The decreased immune system in diabetic individuals makes these infections more severe and more difficult to treat. Multimodal therapy includes vascular and infection management and pressure relief ("offloading").[38,40] Surgical debridement may be necessary.
The images shows the foot of a diabetic patient with three classes of chronic wounds on the same foot: an ischemic third toe, a neuropathic/infected diabetic foot ulcer on the big toe, and a pressure ulcer on the heel from prolonged immobility.
Images courtesy of Nunan R, Harding KG, Martin P. Dis Model Mech. 2014;7(11):1205-13. [Open access.] PMID: 25359790, PMCID: PMC4213725.
When a sore or break in the skin develops in the diabetic foot, it is referred to as a diabetic ulcer. This break opens the protective barrier of the skin, allowing the body to be exposed to infectious organisms.
The first and foremost concern with any new ulcer is infection control.[37-40] Consequently, any patient who develops a diabetic ulcer should seek care from a healthcare provider, who can determine the extent and degree of infection. Patients should be educated about the fact that the lack of pain does not correlate with the extent, degree, and/or severity of the problem.
In addition to infection control, treatments for diabetic ulcers include offloading, surgical debridement, and various wound dressings to enhance wound healing.[37,38] Due to the complexity of the diabetic ulcer, infections can spread and may involve bone (osteomyelitis) or develop into a deep abscess, requiring immediate attention and, possibly, emergent surgical intervention.[38]
Image courtesy of Douglas A Albreski, DPM.
When there is an interruption of blood flow to tissues (typically via infection, vascular dysfunction, or trauma), it causes tissue death, or gangrene.[41,42] The three main types of gangrene are dry gangrene, followed by two infectious types, wet gangrene and gas gangrene (a subtype of wet gangrene). The foot is a common location for the occurrence of gangrene.
Dry gangrene
Dry gangrene is usually noninfectious and occurs when blood flow to a digit or limb is disrupted or suddenly stopped[41,42]—for example, by an arterial clot or a hypothermic injury such as frostbite (shown). Initially, the area becomes a "dusky" or purplish color. Over time, the necrotic or dead tissue separates from the viable or healthy tissue, at which time a well-demarcated line divides these two types of tissue; the necrotic tissue eventually peels away, similar to a healing scab.[43] Management includes restoration of the blood supply to the affected area.[41,43] Surgical intervention is sometimes, but not always, required.[41-43]
Wet gangrene
Wet and gas gangrene constitute medical emergencies: These rapidly spreading infections require prompt diagnosis and almost always require emergent medical and/or surgical treatment. Wet gangrene involves aggressive infection (group A beta-hemolytic streptococci, other streptococcal species, staphylococcal species[41-43]) on the surface of the skin, whereas gas gangrene involves a deeper infection within muscle fibers, in which the organism (usually, but not always, Clostridium perfringens[42]) produces gas bubbles within the limb. Management of wet gangrene includes infection control, surgical debridement and, potentially, amputation.[41-43] Hyperbaric oxygen therapy may facilitate faster wound healing.
Image of fourth-degree frostbite (complete necrosis, dry gangrene, full-thickness tissue loss) of the bilateral feet courtesy of Weaver TL, Robinson D, Frey ES. Eplasty. 2014;14:ic20. [Open access.] PMID: 25165499, PMCID: PMC4106255.
There are three major types of skin cancers: basal cell carcinoma, squamous cell carcinoma, and malignant melanoma. Of these, malignant melanoma is the most aggressive and potentially lethal.[44]
Fortunately, skin cancers that affect the foot are uncommon (3%-15% of all cutaneous melanomas); unfortunately, when skin cancers of the foot do occur, they are usually initially misdiagnosed or have a delayed diagnosis, resulting in a poorer prognosis for the patient.[45] One reason for the difficulty in detecting these lesions is that skin cancers are highly associated with sun exposure; because feet are usually covered by socks and/or shoes, the foot seems to be a less likely location for cancerous lesions, leading to a failure to identify them as such. In addition, these lesions may mimic other foot conditions, such as vascular lesions, ulcerations, warts, and infections.[45]
Any skin abnormality of the foot that does not respond to treatment within a reasonable time frame (eg, 2 months) should be further evaluated to rule out an underlying malignancy.[45] Discoloration or hyperpigmented lesions of the foot should be evaluated to ensure that they are not cancerous.
The primary modality for treating melanoma is surgical excision; early recognition, stage, and management generally have a high potential for cure.[44] Adjuvant therapy includes interferon alpha-2b, checkpoint inhibitors (pembrolizumab, nivolumab, ipilimumab), interleukin-2, BRAF and MEK inhibitors, and chemotherapy.[44]
Images of various presentations of melanoma on the skin of the foot courtesy of Douglas A Albreski, DPM (left) and Bristow IR, de Berker DA, Acland KM, Turner RJ, Bowling J. J Foot Ankle Res. 2010;3:25. [Open access.] PMID: 21040565, PMCID: PMC2987777 (center and right).[45]
As demonstrated in the preceding slides, the feet can be affected by structural, infectious, and systemic changes. These changes can come about at any time, impacting mobility as well as health. A diabetic person on a beach vacation, with loss of feeling, may suffer severe burns on the plantar surface of the foot as he/she walks along the hot sand. An individual wearing high heels to an event may aggravate a bunion. A young person finishing a workout at the gym may walk barefoot in a public shower and become exposed to a fungal infection.
No matter what the event or outing, choosing the appropriate protective footwear can help to prevent some of the conditions that have been discussed. In addition, daily examination of the feet can help to identify as well as prevent complications. Keeping the feet healthy is essential, as healthy feet allow individuals to remain active and avoid painful, unsightly, and even dangerous foot conditions.
The anteroposterior radiograph of the feet was obtained in a woman with rheumatoid arthritis. Signs of metatarsophalangeal instability and osteophytes of both medial cuneometatarsal joints (white arrows) are noted.
Image courtesy of Popelka S, Hromadka R, Vavrik P, Bartak V, Popelka S Jr, Sosna A. BMC Musculoskelet Disord. 2012;13:148. [Open access.] PMID: 22906022 PMCID: PMC3517407.
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