Overview of foot anatomy and biomechanics and assessment of foot pain in adults

INTRODUCTION — Foot pain is a common problem among adults. According to the Framingham population study of older adults, approximately 19 percent of men and 25 percent of women have significant foot pain on most days of the week that often limits their ability to function [1]. The authors of this study recommend that clinicians include a foot examination as part of their routine evaluation of older patients. However, many clinicians may not be adequately prepared to perform such an examination as their training in the diagnosis and care of foot problems is limited [2].

This topic reviews the common causes of foot pain in adult patients, including the frequency of problems in specific populations. Conditions are organized by location, including the forefoot, midfoot, and rear foot. Examination focuses on visual inspection of the foot. The appearance of many common foot conditions can lead the clinician to the correct diagnosis. A detailed approach to the diagnosis of forefoot pain is provided separately. (See "Evaluation, diagnosis, and select management of common causes of forefoot pain in adults".)

EPIDEMIOLOGY AND RISK FACTORS — Certain populations appear to be at increased risk of developing foot pain. These include: older adults, females, patients with obesity, active adults who participate in sports that involve running and jumping, active military personnel, and those engaged in certain occupations [3-8].

In a multiethnic sample of 784 community dwelling adults older than 65 years, 30.9 percent had tenderness to palpation of the foot. In addition, minor foot disorders affected the majority of individuals, including toenail disorders (74.9 percent), minor toe deformities (60 percent), corns and calluses (58.2 percent), and bunions (37.1 percent). Skin problems, including fungal infection, cracking, maceration between toes, and minor cuts, affected greater than one-third of individuals. Sex differences were noted, with women having greater problems with bunions, corns, and calluses. In addition, racial and ethnic differences were noted for flat feet, corns and calluses, toe disorders, and other physical findings, although additional studies would be needed to clarify these findings [3].

Several studies document a significant burden of disability and impaired quality of life among middle aged and older adults with foot pain. In a meta-analysis of 31 studies including 75,505 participants, 24 percent experienced frequent foot pain [4]. Forefoot pain was most common and women appeared affected more frequently than men. In affected individuals, two-thirds reported moderate disability secondary to this pain. In an older cohort of 301 community-dwelling patients aged 70 to 95 years, 36 percent reported disabling foot pain; foot pain had a strong association with depression and low well-being scores on a standardized symptom inventory [5].

Athletes in a number of sports frequently develop foot pain. Among competitive gymnasts, the foot is the most commonly injured area, accounting for 21 percent of all injuries. According to a survey study of 96 club gymnasts, 16.7 percent experienced a stress fracture during a single season, with low back and foot fractures accounting for the majority of injuries [6]. In professional rugby, foot injuries are not as common but lead to substantial loss of playing time. According to a four-year surveillance study, each foot injury lead to an average of 24 days of lost playing time [7]. While 73 percent of injuries are acute, chronic foot conditions such as stress fractures (particularly those of the navicular bone) led to disproportionately greater time lost. In American football, 72 percent of elite collegiate players have experienced a foot or ankle injury, with turf toe and metatarsophalangeal joint dislocation being the third most common of all injuries [9]. Among dancers, ballet performers have the highest injury rates, with foot and ankle problems accounting for 29 percent of injuries in one study of 500 dancers [10]. While evidence is limited, foot and ankle injury rates among field athletes may be higher when playing on artificial turf versus natural grass [11].

ANATOMY AND BIOMECHANICS

Basic foot anatomy — The basic anatomy of the foot is described separately; additional information about foot anatomy and biomechanics related to common foot injuries is provided below. (See "Foot and ankle pain in the active child or skeletally immature adolescent: Evaluation", section on 'Anatomy'.).

Basic foot structures are shown in the following diagrams (figure 1 and figure 2 and figure 3):

●Bones (figure 4 and figure 5 and figure 6)

●Tendons, muscles, and ligaments:

•Medial and plantar foot and ankle (figure 7 and figure 8)

•Lateral foot and ankle (figure 2 and figure 5)

•Dorsal foot (figure 9 and figure 10 and figure 11)

•Plantar foot (figure 12 and figure 13 and figure 14 and figure 15 and figure 16 and figure 17)

●Nerves (figure 18 and figure 19 and figure 20 and figure 21)

●Arteries (figure 22 and figure 23 and figure 24 and figure 25)

Normal foot anatomy can vary significantly among individuals. The longitudinal arch and shorter toes are evolutionary adaptations that allowed humans to run more efficiently for longer distances [12]. Foot shape ranges from short and broad to long and thin, with marked variation in the curvature of the axis from the rear foot to the forefoot (figure 26). Longitudinal arch height can be extremely elevated, as in the cavus foot (picture 1 and picture 2), or flattened to the point where no longitudinal arch exists, as in extreme forms of pes planus (picture 3 and picture 4).

In the longitudinal (sagittal) plane, the foot can be divided into three regions: rear foot, consisting of the talus and calcaneus; midfoot, incorporating all of the tarsal bones; and forefoot, composed of the metatarsals, phalanges, and sesamoid bones (figure 5). In the medial-lateral (transverse) plane, the forefoot can be divided into a medial column and a lateral column. Both are stabilized at the rearfoot through their articulation with the tarsal bones (figure 4). The medial column consists of rays one, two, and three, with a ray defined as the metatarsal and related phalanges. The medial column allows for force transfer during the toe-off part of gait, and the metatarsals and phalanges have greater bulk to accommodate this force. The lateral column is composed of rays four and five and serves more of a sensory function, as the terminal phase of push-off during gait typically leads to forefoot supination. Only the base of the fifth metatarsal absorbs significant weight and force transfer through the attachment of the peroneus brevis tendon and is accordingly thicker and wider than the remainder of the bone.

Accessory ossicles and the variable presence of sesamoid bones contribute to the variability of foot anatomy. Sesamoid bones can exist at the plantar surfaces of the interphalangeal (IP) of the great toe, the first metatarsophalangeal (MTP) joint medial and lateral (hallucal sesamoids), and in the lesser MTP joints [13]. These range in frequency, from hallucal sesamoids, which are always present, to the lesser sesamoids, which are present in 0.1 to 4.3 percent of cases (2 to 13 percent of these exist at the first IP joint). Nine accessory ossicles develop in one of three anatomical areas of the foot. The most common include the os trigone (image 1 and image 2 and image 3), os peroneum (picture 5), and os naviculare, each of which occurs in 20 to 26 percent of feet (table 1).

Foot structure and appearance can vary due to congenital foot conditions. Among the most common conditions are tarsal coalitions, which can manifest a number of patterns among the tarsal articulations. Extreme or rigid pes planus (picture 6) may indicate that a tarsal coalition underlies the shape and appearance of the foot [14]. Another variant that affects the structure, appearance, and function of the foot is brachymetatarsia. This condition can affect any of the metatarsals, which may be abnormally shortened, but the most common are first and fourth brachymetatarsia. Fourth brachymetatarsia occurs in 0.02 to 0.05 percent of individuals (picture 7), but variants of first brachymetatarsia are more common (picture 8). Brachymetatarsia predisposes to a number of pathologic conditions. First metatarsal (MT) shortening may contribute to hallux varus (the opposite subluxation from that seen with the typical bunion) (picture 9) [15-17]. The higher frequency of brachymetatarsia among Special Olympics athletes supports the theory that genetic alterations play an important role in their development [18].

Basic foot structure and biomechanics — The foot functions as both a rigid platform for stance and to absorb the impact of landing during gait and as a flexible lever that enables push-off during walking or running (figure 27). In addition to the distinct anatomical zones of the rear, mid, and forefoot (figure 28), the foot can be divided longitudinally into the functional units of the medial (first through third rays) and lateral columns (fourth and fifth rays), as described above.

In a normal walking gait cycle (figure 27), individuals land on the heel with the foot in supination and Chopart's joint locked to make the foot rigid. After foot strike, the midfoot allows pronation that unlocks Chopart's joint so that individuals can push off the medial column during toe-off. The Lisfranc joint, which lies between the midfoot and forefoot, is a highly stable articulation that supports the transverse arch, while enabling forefoot motion. Stability is provided by the plantar and dorsal transmetatarsal ligaments, a recessed second tarsometatarsal joint crossed by the Lisfranc ligament, the anterior tibialis tendon insertion (which provides additional stability at the dorsal surface), and the posterior tibialis tendon insertions (which provide additional stability at the plantar surface). Thus, with the exception of the second tarsal-metatarsal articulation, the stability of the Lisfranc joint arises from ligamentous and tendon attachments, which allows for slight motion in dorsiflexion and plantarflexion and creates a spring-like action during gait.

The distal articulations of the metatarsals at the MTP joints are highly mobile. Overall, this structural adaptation of a fixed midfoot, slight flexibility at the Lisfranc joint, and great flexibility at the MTP joint allows the midfoot-forefoot complex to act as a powerful lever that can overcome body weight and propel a person forward when running or upward when jumping. During the terminal phase of gait, the forefoot supinates, providing some final assistance with propulsion. The lateral column also provides proprioceptive feedback and additional cushion to the foot. (See "Clinical assessment of walking and running gait".)

Research into transverse arch structure and function has helped to improve our understanding of gait problems in diabetic patients with Charcot foot and individuals with midfoot arthritis [19]. The subtalar joint position helps to determine both the position of the long arch and the ability of the foot to function correctly in a pronation-supination cycle. The mid-tarsal and tarsometatarsal joints are the base of the transverse arch. They must function properly to allow the midfoot to stiffen and store elastic energy that is used during the push-off phase of gait. However, the transverse arch must also retain sufficient motion to allow the longitudinal arch to function like a spring and lever for forward propulsion. Arthritis or neurologic injury, which can cause excessive midfoot stiffness, can impair this essential transverse arch function.

Studies of different foot types have shown that structure affects the ability of the foot to pronate correctly and follow the normal pattern of motion needed during the gait cycle [20]. Other studies indicate that different foot shapes influence the foot strike pattern and determine the areas of the foot that absorb the greatest impact. Cavus feet (picture 1 and picture 2) appear to absorb greater forces during gait (picture 10) [21], and feet with cavus or rear foot varus structures are associated with a higher risk of running-related injury in prospective studies [22]. However, foot structure and gait patterns predict only part of the variability seen in pressure measurements, and these measurements vary at different walking and running speeds. So, while foot structure and shape likely play an important role in injury, gait mechanics play an equally important role and these two clinical parameters must be assessed together.

Longitudinal arch height declines in many patients with age; acquired flat foot syndrome more commonly occurs in middle aged and older adult women. Degenerative tearing of the posterior tibialis tendon is the initial problem in most individuals, but subsequent damage to the spring ligament, talocalcaneal ligaments, and other medial soft tissues can lead to significant deformities [23]. The frequency of forefoot injury in older patients suggests that a similar phenomenon occurs in the transverse arch.

Limited research suggests that wearing high heels predisposes to breakdown of the forefoot. A study of 150 females in low, medium, and high heel groups reported a higher incidence of flattened transverse arch, hallux valgus, and fifth toe varus in the cohort who wore high heels [24].

ANATOMY-BASED APPROACH TO DIAGNOSIS

History — The history of the patient with foot pain focuses on identifying the location of the pain and any common pain pattern suggestive of a particular condition. Important questions to ask include the following:

●Is the pain constant or intermittent?

Constant pain suggests a more severe injury or a medical condition that mimics injury. Intermittent pain occurs in many injuries in which a particular inciting event triggers the condition. As an example, cuboid subluxation causes no pain during normal gait but elicits a sharp pain when walking on an uneven surface causes the cuboid to sublux.

●How would you characterize the pain (eg, dull, sharp, burning)?

Acute injuries to joints or tendons often cause a sharp pain. Dull pain occurs in more chronic conditions. As an example, hallux rigidus causes a chronic dull ache in the first MTP joint, whereas acute turf toe causes a sharp pain affecting the same joint. Burning pain raises suspicion for nerve involvement. A condition like tarsal tunnel often triggers burning pain to the plantar surface of the foot.

●Are there associated symptoms (eg, numbness, paresthesias)?

Numbness and paresthesias in the foot often arise from either spinal cord or peripheral nerve compression; while symptoms affect the foot, the anatomical site of injury is rarely intrinsic to the foot.

●Does the pain radiate?

Radiating pain suggests nerve irritation is the cause of symptoms in the foot. As an example, pain from tarsal tunnel syndrome radiates to the plantar surface of the forefoot and may be felt along the distribution of the tibial nerve. Similarly, pain from Morton neuroma radiates from the metatarsal area where the nerve is injured to the inner aspect of adjacent toes.

●Is there nighttime pain (ie, pain when patient is not bearing weight), or does pain occur only with weight bearing?

Stress fractures and arthritic lesions often cause pain at night. Nocturnal pain may also arise from tumors or conditions such as diabetic neuropathy. Conditions like plantar fasciitis, tendinopathy, and metatarsalgia typically do not cause night pain and usually require weight bearing to elicit symptoms.

●Did the pain develop following a specific injury or a change in sports or work activity (eg, substantial increase in running distance)?

The most common history for overuse injury is a change in sport or work activity that placed increased cumulative stress on the foot. The mechanism of specific acute injuries often indicates the likely diagnosis. As an example, Achilles tendinopathy causing chronic heel pain might stem from the cumulative stress of increased running mileage over a number of weeks, while heel pain from an acute tendon strain might have developed abruptly during a specific speed workout.

●Was there a change in shoe wear before the pain started?

Shoe wear patterns may indicate a change in running gait from weakness, progressive arch collapse, or pain. As an example, the shoes of a runner with excess rear foot pronation and calcaneal valgus might show increased wear on the medial heel and virtually no wear on the lateral edge of the heel.

●Do you have any significant chronic illnesses (eg, diabetes)?

Many chronic illnesses cause symptoms that affect the musculoskeletal system. Diabetes in particular leads to neuropathy that affects the feet and can lead to foot injuries. Gout is another systemic disease that often affects the great and may cause swelling of the first MTP joint without the patient being aware of a specific great toe injury.

●Have you had a significant gain in weight during the past year?

Weight gain affects structures in the foot that provide support during standing or gait. Plantar fasciitis often occurs after a significant increase in weight.

●Does anything relieve the pain?

As an example, many patients with pain from a bunion (hallux valgus) or Morton neuroma get relief simply by wearing a shoe with a wider toe box.

●Is there a family history of foot problems?

Bunions in particular seem to have a relationship to inherited foot structure. The same is true of the conditions that cause brachymetatarsia.

●For women with a recent pregnancy – How much weight gain came with your pregnancy? Did your shoe size change?

During pregnancy, women develop ligamentous laxity related to hormonal changes. Many experience some collapse of the longitudinal or transverse arch, particularly if they have excessive weight gain with a given pregnancy. This may trigger pain across the metatarsal region or along the longitudinal arch.

Examination — Examination of the injured foot begins with close observation. This includes watching the patient's gait as they enter the examination room to see if there is a limp or any other sign of injury. Examine the foot without socks or shoes. Look for swelling, color change, the height and shape of the arch, and any abnormalities or asymmetries, such as abnormal callus patterns on the plantar surface, asymmetry in the forefoot width or arch height, hammering of the toes, bunions or bunionettes, splaying of the toes, or abnormally short metatarsal segments. Such findings may be missed unless the clinician observes the patient's feet while they sit and stand (ie, while weight-bearing), and looks closely at both feet from all perspectives, including the dorsal and plantar surfaces.

Palpation focuses on locating areas of tenderness or warmth, which suggests inflammation. If palpable abnormalities exist, try to ascertain whether they involve soft tissue or bone. Palpation should include both the dorsal and plantar surface. On the dorsal surface, feel for tarsometatarsal bossing (picture 1), which is associated with midfoot arthritis, ganglions (picture 11), and hypertrophy or spurring over the MTP joints (picture 12). On the plantar surface, feel for callus formation (picture 13), and if present determine whether the callused area is tender. Palpate the plantar location of the metatarsal heads. Metatarsal heads that have subluxed through the metatarsal capsules are palpable. If palpable, determine if they are fixed or movable. Palpate for nodules along the plantar arch, tenderness at the calcaneus, and a Haglund deformity at the heel (picture 14). Palpable abnormal bony prominences particularly at the medial or lateral midfoot may represent an accessory ossicle or a tarsal coalition.

Important structures to palpate in the patient with forefoot pain include:

●First metatarsophalangeal (MTP) joint (great toe)

●Fifth MTP joint

●Plantar surface of MTP joints

●Intermetatarsal spaces

●Plantar calluses

●Dorsal proximal interphalangeal calluses

Important structures to palpate in the patient with midfoot pain include:

●Navicular – "N spot" and prominence

●Dorsal tarsometatarsal joints

●Cuboid

●Base of fifth metatarsal

●Plantar fibromas

●Ganglia

Important structures to palpate in the patient with hindfoot pain include:

●Medial insertion of plantar fascia on calcaneus

●Plantar os calcis

●Insertion of Achilles tendon (Haglund deformity)

●Tarsal tunnel

●Peroneal tendons

●Anterior talotibial articulation

●Anterior talus – Lateral corner

●Sinus tarsi

A dynamic assessment is needed to assess normal and abnormal joint motion. Determine whether there are motion restrictions, particularly of the first MTP joint (hallux rigidus is common (picture 12)) and other MTP joints, Lisfranc joint, Chopart's joint, and the subtalar (movie 1) and tibiotalar (ankle) joints. Following trauma or chronic degeneration, excessive joint laxity may be present. Examination of the ankle tendons and ankle joint are discussed separately. (See "Non-Achilles ankle tendinopathy" and "Achilles tendinopathy and tendon rupture", section on 'Physical examination' and "Ankle sprain in adults: Evaluation and diagnosis", section on 'Clinical evaluation'.)

Observe the patient's gait while they walk slowly and then somewhat more quickly, both while they walk toward and away from you. Abnormal foot strike patterns contribute to breakdown of the foot structure. During foot strike, look for calcaneal varus (heel turns inward) or valgus (heel turns outward), marked pronation or supination, and forefoot valgus (foot strike predominantly on the first MTP) or varus (foot strike over fourth and fifth MTP; first MTP often fails to make solid contact). Having the patient walk on their toes may help demonstrate the presence of hallux rigidus, as the patient cannot effectively push off (toe-off) at the end of the gait cycle if the condition is present. Toe walking can help to identify posterior tibial dysfunction, as the condition will limit calcaneal varus. Having the patient walk on their heels may help to identify an unsuspected foot drop or an arthritic tibiotalar joint that prevents dorsiflexion. (See "Clinical assessment of walking and running gait".)

For runners, observe the patient while they run both toward and away from you. The author typically observes running gait initially with the barefoot and then while the patient is wearing their running shoes to see if any degree of correction occurs. When the patient runs in shoes, ask them to start at a slower pace, but then observe them at their normal running pace. Observe whether the increase in speed creates more pronation or supination.

While the examination should look at the entire foot as well as the gait, most problems that cause foot pain affect one of three specific anatomical zones: the forefoot, midfoot, and rearfoot (figure 28). The conditions that occur predominately in each of these zones are listed below.

Forefoot pain — A detailed approach to the diagnosis of forefoot pain is provided separately. (See "Evaluation, diagnosis, and select management of common causes of forefoot pain in adults".)

Midfoot pain — A detailed approach to the diagnosis of midfoot pain is provided separately. (See "Evaluation, diagnosis, and select management of common causes of midfoot pain in adults".)

Hindfoot (or rear foot) pain — A detailed approach to the diagnosis of hindfoot pain is provided separately. (See "Evaluation and diagnosis of common causes of hindfoot pain in adults".)

CAUSES OF FOOT PAIN BY ANATOMICAL REGION

Forefoot clinical conditions — A detailed discussion of the causes of forefoot pain and their diagnosis is provided separately. (See "Evaluation, diagnosis, and select management of common causes of forefoot pain in adults", section on 'Common causes of forefoot pain'.)

Midfoot clinical conditions — A detailed discussion of the causes of midfoot pain and their diagnosis is provided separately. (See "Evaluation, diagnosis, and select management of common causes of midfoot pain in adults", section on 'Common causes of midfoot pain'.)

Rear foot clinical conditions — A detailed discussion of the causes of hindfoot pain and their diagnosis is provided separately. (See "Evaluation and diagnosis of common causes of hindfoot pain in adults", section on 'Common causes of hindfoot pain'.)

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Plantar fasciitis".)

SUMMARY AND RECOMMENDATIONS

●Epidemiology and anatomy – Foot pain is a common problem among adults, particularly older adults, the obese, and active adults who participate in sports that involve running and jumping. An understanding of basic foot anatomy and biomechanics can help with diagnosis. (See 'Epidemiology and risk factors' above and 'Anatomy and biomechanics' above.)

●History – The history of the patient with foot pain focuses on identifying the location of the pain and any common pain pattern suggestive of a particular condition. Important questions to ask are described in the text; most questions are designed to help characterize the pain (onset, provocative factors, palliative factors, quality, radiation, site, timing). (See 'History' above.)

●Key structures to assess by pain location – The diagnosis of many common foot conditions can be made by observation and palpation. Important structures to assess include the following:

•Important structures in the patient with forefoot pain include:

-First metatarsophalangeal (MTP) joint (great toe)

-Fifth MTP joint

-Plantar surface of MTP joints

-Intermetatarsal spaces

-Plantar calluses

-Dorsal proximal interphalangeal calluses

•Important structures in the patient with midfoot pain include:

-Navicular – "N spot" and prominence (picture 15 and picture 16)

-Dorsal tarsometatarsal joints (figure 29)

-Cuboid (picture 17)

-Base of fifth metatarsal (little toe)

-Plantar fibromas

-Ganglia

•Important structures in the patient with hindfoot pain include:

-Medial insertion of plantar fascia on calcaneus (figure 30 and picture 18)

-Plantar os calcis

-Insertion of Achilles tendon (Haglund deformity)

-Tarsal tunnel (figure 31)

-Peroneal tendons (picture 19)

-Anterior talotibial articulation (figure 32 and figure 33)

-Anterior talus – Lateral corner (picture 20 and picture 21 and picture 22)

-Sinus tarsi

●Forefoot pain – The most common area of forefoot pain is the first metatarsophalangeal (MTP) joint. Common conditions seen at the first MTP joint include bunions (hallux valgus), hallux rigidus (degenerative arthritis), and turf toe (forced hyperextension of great toe). Gout commonly affects the MTP and causes acute pain, swelling, and redness around the joint. The second most common area of pain in the forefoot is the plantar surface below the second and third metatarsal (MT) diaphyses, so-called metatarsalgia. Conditions affecting the forefoot and their diagnosis are reviewed in detail separately (table 2 and table 3). (See "Evaluation, diagnosis, and select management of common causes of forefoot pain in adults".)

●Midfoot pain – A common location for midfoot pain is over the dorsum of the articulation of the first tarsometatarsal (Lisfranc) joint, with pain sometimes extending to the articulations of the second and third tarsometatarsal joints. Such pain, particularly following acute trauma, may stem from a fracture or fracture-dislocation. Diagnosis is made by radiograph. Ganglions can develop at the dorsal midfoot and cause more localized pain (picture 11). These can be imaged with ultrasound. Pain can occur along the medial arch.

The navicular bone serves as a keystone for arch stability, and any pain directly over the navicular raises the possibility of serious injury, including navicular stress fractures, tendinopathy of the posterior tibialis tendon insertion onto the navicular, traumatic separation of an accessory navicular, and partial or complete tears of the attachment of the plantar calcaneonavicular (spring) ligament. Pain over the navicular with an unusual bony prominence suggests a possible accessory navicular, whereas pain over the plantar surface of the arch can arise from an acute strain or longitudinal arch collapse.

Tenderness at the base of the fifth MT suggests injury and warrants imaging with plain radiographs, as these injuries can be difficult to diagnose and manage. A table summarizing diagnostic considerations in the patient with midfoot pain is provided (table 4). (See "Evaluation, diagnosis, and select management of common causes of midfoot pain in adults".)

●Hindfoot pain – The most common location of hindfoot pain is at the insertion of the plantar fascia into the medial aspect of the calcaneus, a location that suggests plantar fasciitis. Most patients with plantar fasciitis describe intense pain when they first step out of bed in the morning. Pain is severe when they begin walking or running, but gradually subsides with activity. Dull pain often persists throughout the day. Pain is relieved by sitting but grows more intense whenever they stand or walk. Night pain is not typical. Examination findings usually include tenderness at the medial insertion of the plantar fascia into the calcaneus.

The diagnosis of other rear foot conditions is suggested by the location of pain and tenderness, such as the os calcis on the plantar surface of the heel or the insertion of the Achilles tendon, which suggests distal tendinopathy or enthesopathy. A table summarizing diagnostic considerations in the patient with rear foot pain is provided (table 5). (See "Evaluation and diagnosis of common causes of hindfoot pain in adults".)