Juvenile idiopathic arthritis

The foot and ankle joints are most often affected in all subtypes of juvenile idiopathic arthritis. Children may present with a limp or reluctance to walk. In the hindfoot, pain and inflammation can lead to valgus deformity (in two‐thirds of cases) or varus deformity (in one‐third of cases). In some patients, this may progress to bony ankylosis. The child may be reluctant to push off with the forefoot during walking, and pressure studies show poor contact of the foot to the floor. Lack of use can lead to delayed maturation of bone or soft tissue, and routine examination should include an assessment of leg length discrepancy.

Morton’s neuroma (interdigital neuroma)

This normally affects the proximal part of the plantar digital nerve and accompanying plantar digital artery. Trauma to these structures leads to histological changes, including inflammatory oedema, microscopic changes in the neurolemma, fibrosis and, later, degeneration of the nerve. Morton’s neuroma is the result of irritation or compression of the interdigital nerve.

Clinical features – Clinical features include a gradual onset, with sudden attacks of neuralgic pain (burning) or paraesthesia during walking, often in the third and fourth toes. Examination may show lesser toe deformities, slight splaying of the forefoot, abnormal pronation and hallux valgus. These often occur in people who wear footwear with a narrow toe box or those who undertake sporting activities with increased movement in the forefoot. Compression of the cleft or laterally across the metatarsal heads may produce acute pain and the characteristic ‘Mulder’s click’.

Treatment – An ultrasound scan is the most useful diagnostic tool. Patients should be given advice about suitable footwear and the provision of orthoses to address abnormal foot function. Treatment is with injections of local anaesthetic and hydrocortisone into the interdigital space, or surgical excision if this fails.

Stress fracture (march fracture)

Stress fractures are associated with increased activity, and lesions can affect any of the metatarsal shafts (Figure 7.4), often along the line of the surgical neck. They can occasionally be seen in patients with osteoporosis as a pathological fracture. Other common sites of stress fractures in the foot include the navicular and the calcaneus.

Clinical features – Patients will often report an increase in the frequency, duration or intensity of activity or exercise they undertake, which may coincide with a change in occupation or footwear. The symptom is a dull ache along the affected metatarsal shaft, which changes to a sharp ache just behind the metatarsal head. The pain is exacerbated by exercise and is more acute at ‘toe off’. Tenderness and swelling are felt over the dorsal surface of the shaft. Pain is produced by compression of the metatarsal head or traction of the toe. X‐ray examination may not show the fracture for up to 6 weeks, but if it is important to confirm the diagnosis, for example, for an athlete who needs advice on whether to continue playing sport, a bone scan or MRI can reveal it earlier.

Treatment – Rest and local immobilization are usually enough; the use of an Aircast boot allows mobilization during this period and is usually required for 6 weeks. These fractures rarely require casting or surgical fixation.

Acute synovitis

This condition is normally associated with acute trauma, which leads to inflammation of the synovial membrane and effusion. Freiberg’s disease (avascular necrosis of the second metatarsal head) may also contribute. Systemic causes of acute synovitis, such as rheumatoid arthritis (Figure 7.5) or infection, should be excluded when making a diagnosis.

Clinical features – It is rare in children but often affects young adults in puberty. Patients complain of a sudden onset of painful throbbing that is made worse by movement. The patient may have experienced trauma or infection or have a systemic inflammatory disorder. Any movement of the joint produces pain. Fusiform swelling is present around the distended joint, and crepitus may be felt.

Treatment – Rest, immobilization and ultrasound treatment may help if trauma is the cause. Anti‐inflammatory drugs sometimes help. Previously unsuspected systemic arthritis, such as psoriatic arthritis, should be investigated.

Differential diagnosis: inflammation of anterior metatarsal soft tissue pad

This common condition is generally found in middle‐aged women. It affects the soft tissues of the plantar aspect of the forefoot and is associated with increased shear forces, such as occur when wearing ‘slip‐on’ and high‐heeled court shoes.

Clinical features – Patients present with a burning or throbbing pain localized to the soft tissues anterior to the metatarsal heads. The pain usually develops over a few weeks, is often associated with walking in a particular pair of shoes, and is usually relieved by rest. The tissues are inflamed, warm and congested. Direct palpation, rotation and simulation of shear forces on the foot exacerbate the pain. Examination of patients’ shoes may reveal a worn insole, with a depression under the metatarsal heads.

Management – Advice on footwear, with adequate support or cushioning, should be given. Associated abnormal pronation or lesser toe deformities should be corrected with orthoses.

Plantar metatarsal bursitis

This condition may affect the deep anatomical or superficial adventitious bursae. In the acute form, such as in dancers, squash players or skiers, the first metatarsal is usually affected, while the second to fourth metatarsals are predominantly affected in chronic inflammatory arthritis.

Clinical features – Patients present with a throbbing pain under a metatarsal head that usually persists at rest and is exacerbated when the area is first loaded. The acute condition affects men and women equally, usually in younger adults. If a superficial bursa is affected there will be signs of acute inflammation, with fluctuant swelling and warmth. With deep bursitis, the tissues are tight and congested. Direct pressure or compression produces pain, as does dorsiflexion of the associated digit.

Treatment – Anti‐inflammatory drugs are useful; in practice, local gels and systemic oral drugs help. Injections of corticosteroid may be indicated in severe cases. Patients must rest the affected part; this may be achieved by immobilization of the forefoot (rocker‐soled shoe or Aircast). Any underlying deformity or foot type with abnormal function should be assessed and treated.

A summary of causes of pain in the forefoot is presented in Box 7.3.