How common is foot pain?

Pain in the foot is a common complaint. Garrow et al (2004) in a survey of almost 5000 people found that 9.5% had disabling foot pain. Some studies have shown higher incidences: 14% in adolescents (Spahn et al 2004), rising to 36% in older patients (Menz et al 2006b). The incidence of foot pain increases with particular foot deformities or pathologies. Ribu et al (2006) found that 75% of patients with diabetic foot ulcers had foot pain from these ulcers, which may come as a surprise to many practitioners who believe that neuropathic ulcers are always painless.

Foot deformity is thought to be a common cause of foot pain. The evidence from the literature to support this hypothesis is variable. With certain deformities there is a strong correlation, such as pes cavus. A recent study found that 60% of subjects with this structural deformity had foot pain (Burns et al 2005). Hallux valgus and lesser toe deformities were not found to be a significant cause of foot pain in an elderly population (Badlissi et al 2005) but this is in contrast to the work of Benvenuti et al (1995) who found a significant relationship between pain and these and other foot pathologies such as plantar calluses and pes planus in a similarly aged population.

When considering foot deformity and its association with pain, one issue is the degree of deformity. It would be natural to assume that the bigger the deformity the more pain the patient would experience. However, this is not the case and has been demonstrated with several foot deformities, most recently hallux valgus. Thordarson et al (2005) found that the degree of pain experienced by patients waiting for hallux valgus surgery had no correlation with the degree of deformity measured clinically or radiologically. Such evidence reinforces the subjective nature of pain. However, this does not mean that foot deformity is not a major cause of morbidity. Even in those with foot deformity and no foot pain there is still the potential for significant other pathology and morbidity. Foot deformity, especially lesser toe deformities and hallux valgus, has been shown to increase the risk of falls in the elderly (Menz et al 2006a). Pes planus has been shown to increase the incidence of osteoarthritis in the knee and pes cavus has been shown to increase the incidence of osteoarthritis of the hip (Reilly et al 2006). Foot deformity is a known risk factor for foot ulceration in patients with diabetes and rheumatoid arthritis.

Examination of the patient with foot pain

You should first observe the patient, not the foot. It is useful to highlight those traits that have been discussed under medical history (Ch. 5) as the source of pain may be explained by general disease processes. Assess the patient’s attitude. This may reveal psychological variations from normal and may influence your assessment strategy and the outcome of any treatment. Pointers concerning general health include the following:

The physical examination may reveal findings that raise concerns. For example, a manual worker who has thick calluses on his hands, and yet says he cannot work because of the pain in his foot, may be being less than fully honest.

Examination of the foot begins with watching the patient walk (see Ch. 10). An antalgic limp, where the patient will spend only a short period of time on the painful foot, is a clear positive sign. The limp may be linked with other problems associated with proximal joints or the back; these should be excluded. Look at shoe wear on the sole; this may indicate an abnormal gait pattern. Are the toes severely clawed, possibly suggesting a neurological problem? It is important to note any callosities, both dorsally and on the sole, as these indicate areas of high pressure and friction. Similarly, one must remember all the structures running under any area of tenderness.

The sources of pain are numerous and can be subdivided for convenience into problems affecting different tissues, different regions of the foot, generalised disorders and referred pain. Table 17.1 provides an overview of pathologies by tissue type which may cause foot pain. Tables 17.2–17.4 cover the common, less common and conditions not to be missed that can be the source of pain in the forefoot, midfoot and rearfoot respectively. In many cases the origins are not clear and assessment and further investigations are necessary to isolate the cause. The practitioner must always remember that multiple conditions may co-exist either in isolation or by association through compensation, for example a patient with a painful bunion may develop a Morton’s neuroma through transfer metatarsalgia. It is important to identify these potential causal links as they can assist in the diagnosis and subsequent management of multiple conditions.

Table 17.1 Causes of foot pain by anatomical structure

Table 17.2 Conditions that can cause forefoot pain

Table 17.3 Conditions that can cause midfoot pain

Table 17.4 Conditions that can cause rearfoot pain

It is important to localise the current pain/symptoms to specific anatomical structures. Manikin diagrams or photographic pain maps (Fig. 17.1) are helpful in documenting this more quickly than is possible in words and provide a useful reference for future when the character or site of the pain changes over the course of treatment. The description of current pain/symptoms should be supplemented by an attempt to identify the precise structures affected and to reproduce the symptoms if appropriate either by direct palpation or by movement of the affected parts. The character of the symptoms (numbness, fatigue, pain), and, as appropriate, the pain characteristics (e.g. burning, bruised, achy) should be explored. Any influencing factors, for instance the effect of weightbearing/non-weightbearing activity, diurnal variation, footwear types will also help to identify whether local mechanical factors might be driving the pathology. Previous treatments should be explored in detail, both as a pointer to the disease process and to avoid duplicating mistakes or ineffectual treatments.

Figure 17.1 Pain map.

Having prompted the patient to describe the symptoms themselves it is appropriate also to gauge the impact of the symptoms on the patient and their daily life. This can be done in several ways the most common being to use visual analogue scales to quantify simply pain or other aspects of impairment. It has long been common practice to record this sort of information empirically but more recently there has been a burgeoning of approaches designed to explore this in a more structured way and to quantify the degree of impact. These are the so-called patient reported measures of health status or health-related quality of life. A variety of measures are available such as Garrow’s Manchester Foot Pain and Disability Questionnaire (MFPDQ) (Garrow et al 2000) and Bennett’s Foot Health Status Questionnaire (Bennett et al 1998, Bennett & Patterson 1998) (see Ch. 4). Patient-reported measures can be generally applied to all foot problems such as the two above or may be specific to diseases (such as the Leeds Foot Impact Scale for rheumatoid arthritis (RA)) (Helliwell et al 2005). The advantage of documenting the impact of symptoms formally is that it establishes a baseline against which the success of future treatment can be gauged and it also acts as a comparator with other groups.

Articular conditions

Osteochondroses

Osteochondral defects

A common articular injury is an osteochondral lesion or defect. These can be seen in any joint following a traumatic injury but are most often seen on the posteromedial or anterolateral aspects of the trochlear surface of the talus following an ankle sprain (Fig. 17.2). Other common sites include the first metatarsal head and the tibial plafond. Osteochondral lesions can be graded from I to IV (Table 17.5) and this helps dictate management. Classical symptoms are constant articular pain and stiffness with some swelling. Catching or locking can occur with grade III or IV lesions. Some residual pain and stiffness is often present and the patient should be counselled that early arthritis is likely to develop in the joint. Acute symptoms will be those of a sprained ankle, with the patient complaining of pain, swelling and difficulty walking. Chronic symptoms are more general, with patients complaining of discomfort, pain and perhaps stiffness during or after exercise. If an osteochondral fragment has become detached from the talar dome, then there may be locking and giving way in the ankle, suggestive of a loose body:

• Investigations (see Table 17.5)

Figure 17.2 Osteochondral defect of the talus.

Table 17.5 Classification of osteochondral lesions

Grade of lesion	Description	Imaging investigation required for diagnosis
I	Subchondral cystic lesion with intact roof (also known as articular bone bruise)	Magnetic resonance imaging (MRI)
II	Subchondral cystic lesion with communication to joint surface	Computed tomography (CT)/MRI (may be visible on X-ray)
III	Separate non-displaced chondral lesion	CT/MRI/X-ray
IV	Displaced chondral lesion	CT/MRI/X-ray

Plain X-rays should initially be requested but in the acute stage X-rays may appear normal, especially if the lesion is stage I, i.e. only the articular cartilage is damaged (Berndt & Harty 1959). Even in a chronic lesion it may be difficult to detect any changes on plain X-ray. Magnetic resonance imaging (MRI) is the most sensitive, as well as the most expensive way of demonstrating the osteochondral fractures. Blood tests are of no value in the investigation of this condition.

• Differential diagnosis

Acutely, this will be the co-existent trauma. Chronically, it will be other joint conditions such as capsulitis or synovitis. Around the ankle bony impingement, tendon or syndesmosis injuries should be suspected along with early OA.

Osteochondritis desiccans

Osteochondritis desiccans is triggered by avascular necrosis and is also termed osteonecrosis. It is most commonly seen in adolescents but can also occur in adults. It has been reported that trauma, either acute or chronic, is the cause in 50% of cases and the remainder is due to vascular compromise. There is still much we do not know about the aetiology of this condition. The bone most commonly affected is the lesser metatarsal (Freiberg’s), followed by the navicular (Köhler’s in children or Mueller–Weiss syndrome in adults), and then the cuneiforms (Bushke’s disease).

Freiberg’s

This is most commonly seen in the second metatarsal between 13 and 18 years of age and there is a female to male preponderance of 5 : 1. Symptoms include localised pain often with swelling of the affected MTPJ, and which is aggravated by weightbearing activities. Palpation of the joint and passive movement, especially plantarflexion, produce pain. Confirmation and staging of the condition can be confirmed on X-ray.

Köhler’s or Mueller–Weiss syndrome

The paediatric form of this condition is most commonly seen in boys (6 : 1 male to female ratio) aged between 3 and 9 years. It is characterised by localised pain and swelling around the dorsal aspect of the navicular with warmth. The child often limps. In the adult form, the condition is usually more chronic in presentation with similar localisation of the pain and swelling but often with crepitus of the talonavicular joint and the development of a flatfoot posture. X-rays are used to confirm the presence of either form.

Buschke’s disease

This rare condition can affect any of the cuneiforms. It occurs in children aged 5–13 years and is thought to be more prevalent in cavus feet. It is difficult to diagnose due to lack of localised swelling or erythema and initial X-rays are often negative.

Traction apophysitis

This condition is only seen in children either in the heel (Sever’s disease) or at the base of the fifth metatarsal (Iselin’s disease). It is caused by excessive traction of soft tissue on a secondary centre of growth before these centres have fused with the main body of the bone.

Sever’s disease

This condition occurs usually between the ages of 10 and 15 years in athletic children. It used to be seen more commonly in boys but is now seen equally between sexes probably due to more girls playing sport. It is often associated with periods of rapid growth. The pain may be localised either posteriorly due to contracture of the Achilles or inferiorly due to contracture of the plantar fascia and intrinsic musculature. The presence of a tight Achilles and a flatfoot posture has also been highlighted as contributory factors. There is an absence of swelling but localised tenderness to palpation is the key to diagnosis. X-rays and other imaging modalities are not diagnostic.

Iselin’s disease

This is not a commonly encountered condition. Pain is localised to the peroneus brevis insertion at the base of the fifth metatarsal, usually plantar-lateral, with minimal swelling. The epiphysis appears between the ages of 10 and 12 and fuses 2–3 years later. Stress testing of the peroneals can induce the symptoms. X-rays can be helpful to exclude fracture and are often characterised by fragmentation of the epiphysis.

Tarsal coalition

This is a congenital condition, inherited as an autosomal dominant trait, in which adjacent tarsal bones have a fibrous, cartilaginous or bone connection or bridge which progressively restricts normal movement. This may be termed syndesmosis, synchondrosis or synostosis, respectively, and occurs in less than 1% of the population (Lemley et al 2006). Generally, it begins as a fibrous union in infancy and progresses to cartilaginous and then bony union; however, it may remain fibrous. The most common coalition is the talocalcaneal, followed by calcaneonavicular (Lemley et al 2006), and these account for 95% of all coalitions. Although rare, most other possible combinations have been described.

Although these coalitions usually ossify between 8 and 16 years, symptoms may not develop until late childhood or into adulthood. Sometimes patients never develop symptoms and the diagnosis is made incidentally. When they do present, patients may complain of pain and stiffness around the hindfoot. The onset of initial symptoms is frequently after an ankle sprain and this often leads to inappropriate management. It is believed that the trauma of the ankle sprain triggers an inflammatory reaction around the coalition. Stiffness in the subtalar or midtarsal joint movements is usually the predominant sign. Patients may also have a valgus flatfoot with subtalar irritability, characterised by pain on forced plantarflexion of the ankle joint and some peroneal spasm. Tarsal coalition is the commonest cause of peroneal spastic flatfoot.

Appropriate plain X-rays may demonstrate a coalition; DP, lateral and medial oblique films should be taken. Medial oblique views show the calcaneonavicular coalition (Fig. 17.3). A Harris axial view may show a talocalcaneal coalition. Dorsal beaking on the head of the talus is a secondary change to abnormal movement, also suggesting this type of pathology (Case history 17.1). A long anterior calcaneal process may indicate a calcaneonavicular coalition on the lateral view. If X-rays are not diagnostic, a CT scan or MRI are the imaging modalities of choice to confirm the diagnosis.

Figure 17.3 X-ray illustrating calcaneonavicular coalition (arrow) – medial oblique view.

Rheumatoid arthritis

RA is a systemic, inflammatory joint disease with an overall prevalence of about 0.8%. It is twice as common in females and usually presents in the fifth decade of life. The disease can lead to disabling pain with significant functional limitation associated with severe joint destruction and deformity. However, the course and severity of the disease varies widely and is often difficult to predict. The foot is affected in 90% of cases.

The diagnosis of RA is a clinical one based on observation of factors over a 6-week period (Table 17.6). The disease usually presents with morning stiffness, pain and swelling of the small joints of the hands and feet. It is estimated that RA first presents in the feet in 20% of cases. This is a key feature for podiatrists and other healthcare practitioners interested in the foot as many patients presenting with foot pain may have undiagnosed RA. This has led to the development of an early referral algorithm for RA (Emery et al 2002) which recommends immediate referral in the presence of:

Table 17.6 Components of an assessment

Clinical features vary significantly depending on the severity of the disease, the location of symptoms, and whether the disease is early or established in duration. In the early stages of the disease the presenting symptoms are usually morning stiffness, pain and swollen joints. As the disease progresses foot deformity follows and this maybe the presenting feature in conjunction with painful swollen joints, calluses and ulceration. A pes planovalgus foot deformity is present in 50% of patients usually due to a combination of talonavicular or subtalar involvement often with tibialis posterior dysfunction. The ankle is less frequently affected.

Hallux valgus is present in up to 60% of established rheumatoid cases. The bunion deformity often pushes the lesser toes into either a hammered position, or more commonly causes lateral or ‘fibula deviation’ of the toes in the transverse plane. Another common presenting symptom may be pain localised to two of the lesser toes associated with splaying of the digits termed Jacobs’ daylight sign (Fig. 17.4). This is due to MTPJ synovitis in association with an intermetatarsal bursitis or other space-occupying mass such as a rheumatoid nodule. The localised inflammation often leads to neuroma symptoms due to irritation of the digital nerve and this may be the presenting complaint (see Case history 17.2).

Figure 17.4 The Jacobs’ daylight sign affecting the left second and third toes. Note the significant swelling of the contralateral ankle.

Psoriatic arthritis

Psoriatic arthritis (PA) is classically a seronegative enthesopathy with a small and large joint proliferative arthritis. It is estimated that between 1% and 2% of the population have psoriasis and approximately 10% of these will go on to develop PA. There are many forms of psoriasis but there does not appear to be any correlation with a particular form and the development of PA.

Oligoarticular (several joints) or monoarticular (single joint) arthritis is the classical presentation of this condition. The pattern of involvement usually affects the interphalangeal joints in an asymmetric manner. A chronically swollen toe or finger is a common feature (Fig. 17.5). This is called dactylitis or sausage toe. Contrary to historical teaching, the foot and ankle is the most common site for PA (Hammerschlag et al 1991). The patient usually presents with painful joint(s) in the forefoot often with heel pain due to enthesopathy and tendon involvement such as tibialis posterior tendinopathy.

Figure 17.5 ‘Sausage fourth toe’ due to psoriatic arthritis.

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