Examination of the foot and ankle

Understanding the correct terminology is crucial, explain Mr Steve Lipscombe and Dr Dan Bunstone.

Hallux valgus (shown above) presents with a bunion over the great toe, which is angled laterally (Photograph: SPL)
Hallux valgus (shown above) presents with a bunion over the great toe, which is angled laterally (Photograph: SPL)

Examination of the foot and ankle can vary depending on whether the examination is of a 'normal' foot and ankle or one with dramatic foot and toe deformity, for example caused by rheumatoid arthritis.

Diabetic neuropathy can result in ill-defined burning pains across the foot or Charcot joint. Diabetic foot care is critical, as uncontrolled infection in an insensate foot can result in amputation.

The terminology used in the examination of the foot can be confusing, leading to problems with diagnosis and subsequent management. The combination of movements around the ankle, hindfoot (heel area), midfoot (primarily across the dorsum of the foot), and forefoot (great and lesser toes) can also be difficult to understand.

The foot as a tripod
Imagine the normal foot as a tripod with weight being distributed between the heel, great toe and fifth toe. With the patient standing, the heel should sit in the line of the lower leg, the medial arch of the foot should be visible and the toes should be more or less straight and sitting comfortably on the floor.

Common conditions include flatfoot (pes planus) when the medial arch of the foot is lost. Typically this progresses with the heel tilting into valgus (a planovalgus foot) so that the patient appears to be weight bearing along the medial border of the foot.

Alternatively, the arch of the foot is exaggerated (pes cavus) with clawing of the toes. It is important to inspect the foot with the patient standing and then walking to see the deformities. This inspection of the foot along with the patient's age is key to reaching the diagnosis.

Flatfoot
In young patients, flat feet are usually idiopathic and of no consequence. The key feature is whether the flat foot is correctable and pain free.

Establish the medial arch by extending the big toe with the patient standing. Ask the patient to go up on tip-toes (heel raise test). The heel should tilt into varus (towards the midline). Fixed painful flatfoot in a young patient is commonly caused by tarsal coalition, typically calcaneonavicular coalition.

In middle-aged patients, tibialis posterior dysfunction occurs with initial pain along the course of the tendon around the back of the medial malleolus.As the tendon fails, a planovalgus deformity occurs.

Assess tibialis posterior by palpating along its course. Grip the lower leg and with the foot hanging down ask the patient to move the foot to touch your hand positioned 5cm towards the midline level with the great toe. Ask them to hold it there as you attempt to push the foot away, at the same time feeling along the course of the tendon. Inability to move the foot, resist your hand's action or pain along the course of the tendon suggests tendon dysfunction.

In an older patient, degenerative arthritis of the mid and hindfoot can produce the same pattern, commonly as a sequalae to tibialis posterior dysfunction. Pain is present on movement and palpation of these joints and typically bony prominences (cheilus) will be present.

Toe deformity
Typically, you will see toe deformity in a middle-aged woman presenting with a bunion over the great toe, which is angled laterally (hallux valgus).

This produces pain over the bunion but also underneath the metatarsal heads as weight transfer is disturbed due to pain and the rotating great toe.

Sometimes a dorsal cheilus due to osteoarthritis of the great toe (hallux rigidus) can be confused for a bunion, although the two can coexist.

The lesser toes can deform (mallet, hammer and clawing) in isolation or with associated hallux valgus causing rubbing and painful callosities in footwear.

The mallet deformity affects only the distal joint. The other two deformities can be confused.

Essentially the clawed toe has hyperextension of the metacarpophalangeal joint.

Ankle instability
Symptoms of instability can occur in the ankle. For a young patient consider hyperlaxity. Trauma to the ankle can produce lateral ligament complex injury and, uncommonly, subsequent instability.

Ankle stability can be difficult to assess. Pain along the lateral ligament complex is not specific. Anterior drawer testing can also be difficult. With the patient sitting, grip the heel and try to position it so that it sits in line with the lower leg with the foot slightly plantarflexed. Now grip the tibia and attempt to move the hindfoot towards you noting any anterior drawer when compared with the other limb.

Alternatively, injury to the articular cartilage can produce a painful osteochondral defect. Assess ankle movements by placing your forearm along the bottom of the foot and moving as one upwards and then downwards. Anterior impingement suggests a cheilus. Lateral impingement can also occur with chronic ankle injury. Palpate along the tendo-achilles. Swelling or tenderness suggests tendinopathy.

Other common diagnoses
The plantar fascia is a tough fibrous sheet that helps form the medial arch. Tenderness is typically felt along the medial arch of the foot with point tenderness on the medial aspect of the heel. Patients typically report worse pain on getting out of bed in the morning.

Arthritic change in the foot will produce pain. Assess the subtalar joint by gripping the ankle firmly with one hand then twisting the heel with the other. Now grip the heel and adduct then abduct the midfoot to provoke pain in the arthritic Chopart joints.

Assess the sesamoid bones for point tenderness directly under the base of the great toe. Dorsal cheilus of the great toe will produce a stiff toe with dorsal impingement. Pain throughout occurs in more advanced osteoarthritis. Morton's neuroma produces paraesthesia in the digits and a painful spot between the metatarsal heads.

  • Mr Lipscombe is an orthopaedic registrar in Merseyside and Dr Bunstone is a GP principal in Cheshire.

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