Orthopaedic Surgery - Flatfoot

Basics

Flatfoot, or pes planus, is a condition in which the normal medial longitudinal arch of the foot is reduced or absent.

It may be an asymptomatic normal variant or a painful deformity caused by an underlying structural, neurologic, inflammatory, degenerative, or tendon-related disorder.

Normal Development

A flat-appearing foot is common in infants and young children because the medial longitudinal arch is not yet fully developed.

Physiologic flatfoot may therefore be normal up to approximately 5 years of age.

Classification

Flatfoot can be classified according to flexibility and according to whether it develops during childhood or adulthood.

Flexible Flatfoot

A flexible flatfoot demonstrates loss of the medial arch during weight bearing.

The arch reappears when the patient is non-weight bearing or rises onto the toes.

The hindfoot remains mobile and its valgus alignment can generally correct toward neutral or varus.

Rigid Flatfoot

A rigid flatfoot lacks a normal medial arch both during weight bearing and when the foot is unloaded.

Hindfoot motion is restricted, and valgus deformity does not correct with toe standing.

Rigid flatfoot is more likely to reflect an underlying structural abnormality.

Pediatric Versus Adult Flatfoot

The age at onset provides important diagnostic information.

Pediatric flatfoot is commonly developmental or congenital, whereas adult-onset deformity more often results from posterior tibial tendon dysfunction, arthritis, neuropathic disease, or previous trauma.

Epidemiology

Congenital Flexible Flatfoot

Flexible flatfoot commonly runs in families, although the precise inheritance pattern is uncertain.

Persistent flexible flatfoot has been reported in approximately 14% of adults.

Tarsal Coalition

Tarsal coalition is an important cause of congenital or developmental rigid flatfoot.

Some forms demonstrate familial inheritance, classically described as autosomal dominant with variable penetrance.

Reported prevalence varies widely, from less than 1% to more than 10%, partly because many cases remain asymptomatic.

Adult-Acquired Flatfoot

Posterior tibial tendon dysfunction is one of the most common causes of acquired flatfoot in adults.

The exact population incidence is uncertain.

Risk Factors

Flexible Pediatric Flatfoot

A positive family history increases the likelihood of persistent flexible flatfoot.

Tarsal Coalition

Family history is an important risk factor for tarsal coalition.

Some reports have also described a higher frequency in females.

Posterior Tibial Tendon Dysfunction

Risk factors for adult-acquired flatfoot related to posterior tibial tendon degeneration include hypertension, diabetes mellitus, obesity, and previous trauma.

Other Predisposing Conditions

Additional disorders associated with flatfoot include a tight Achilles tendon, neurologic or neuromuscular disease, inflammatory arthritis, osteoarthritis, post-traumatic arthritis, and Charcot neuroarthropathy.

Neurologic causes may include conditions such as spina bifida, myelodysplasia, stroke, or other disorders affecting muscle balance and foot mechanics.

Etiology

Congenital Flexible Flatfoot

Flexible pediatric flatfoot is usually developmental and may have a familial predisposition.

Tarsal Coalition

Tarsal coalition results from abnormal congenital connection between two or more tarsal bones.

The connection may be fibrous, cartilaginous, or osseous.

Posterior Tibial Tendon Dysfunction

Adult-acquired flatfoot commonly results from degeneration, attenuation, elongation, or rupture of the posterior tibial tendon.

As tendon function deteriorates, the medial arch progressively collapses and the hindfoot drifts into valgus.

Charcot Neuroarthropathy

Flatfoot resulting from Charcot neuroarthropathy develops because of bone fragmentation, resorption, fracture, joint instability, and progressive collapse.

Other Causes

Other important causes include congenital vertical talus, peroneal spastic flatfoot, previous trauma, and severe structural deformity.

Diagnosis

Signs and Symptoms

The most obvious feature is a low or absent medial longitudinal arch.

Some patients remain completely asymptomatic.

Others develop pain, fatigue, swelling, or progressive deformity.

Pain

Pain is commonly felt along the medial arch or medial ankle.

Symptoms may worsen with prolonged walking, sports, high levels of activity, or following trauma.

Progressive Deformity

Some forms of flatfoot gradually worsen with time, particularly adult-acquired flatfoot related to posterior tibial tendon dysfunction.

Shoe Wear

Abnormal loading may produce increased wear along the medial aspect of the shoe.

History

The history should establish age at onset, progression, family history, activity level, previous trauma, neurologic or systemic disease, and associated pain or swelling.

Pediatric History

Pediatric flexible flatfoot is often noted from an early age.

Parents may report fatigue, decreased endurance, difficulty participating in sports, or pain after prolonged activity.

Adult-Acquired Flatfoot

Posterior tibial tendon dysfunction commonly presents as gradually progressive aching and swelling along the medial ankle and foot.

With progression, the foot may flatten and abduct, and walking becomes increasingly difficult.

Physical Examination

Determining Flexibility

The most important initial examination step is determining whether the flatfoot is flexible or rigid.

This distinction substantially narrows the differential diagnosis and influences treatment.

Rigid Flatfoot

In rigid flatfoot, the medial longitudinal arch remains absent during both weight bearing and non-weight bearing.

Hindfoot motion is limited, and the valgus deformity does not correct when the patient rises onto the toes.

Flexible Flatfoot

In flexible flatfoot, the arch disappears during standing but reconstitutes when the foot is unloaded or during toe standing.

The hindfoot remains mobile and usually moves from valgus toward neutral or varus with heel rise.

Forefoot Abduction

Increasing deformity may produce lateral deviation of the forefoot relative to the hindfoot.

This creates the characteristic “too many toes” sign when the patient is viewed from behind.

Posterior Tibial Tendon Examination

Resisted Inversion

Strength of inversion should be tested against resistance.

Weakness or inability to invert the foot may indicate posterior tibial tendon dysfunction.

Single-Leg Heel Rise

The patient is asked to rise onto the toes while standing on the affected limb.

Pain, weakness, inability to perform the maneuver, or failure of the hindfoot to move into varus suggests posterior tibial tendon insufficiency.

Inspection and Palpation

The foot should be inspected for arch collapse, hindfoot valgus, forefoot abduction, swelling, callosities, and asymmetry.

Tenderness should be localized carefully, particularly along the posterior tibial tendon, subtalar region, midfoot, and medial arch.

Gait Examination

Gait should be observed for pain, weakness, or abnormal propulsion.

Antalgic Gait

A painful limp may suggest arthritis, tendon inflammation, stress injury, or another painful structural disorder.

Posterior Tibial Tendon Dysfunction

Patients with posterior tibial tendon dysfunction may demonstrate reduced push-off and impaired propulsion.

Neurologic Gait

An awkward or foot-slapping gait raises concern for an underlying neurologic or neuromuscular disorder.

Achilles Tendon

The Achilles tendon should be assessed for tightness.

Limited ankle dorsiflexion caused by gastrocnemius-Achilles contracture can worsen a flatfoot deformity and contribute to symptoms.

Imaging

Weight-Bearing Radiographs

Imaging should be obtained while the patient is standing whenever possible because deformity is best appreciated under physiologic load.

Standard evaluation may include weight-bearing AP, lateral, and oblique views of the foot, with ankle views when ankle or hindfoot pathology is suspected.

Calcaneal Pitch

The calcaneal pitch decreases as the medial longitudinal arch collapses.

In severe flatfoot it may approach 0°.

Talus–First Metatarsal Angle

The relationship between the talus and first metatarsal can be assessed on weight-bearing radiographs.

Normally, these structures are nearly collinear.

Increasing angular divergence reflects progressive arch collapse.

Severity

Historically, an angle of approximately 15° or less has been considered mild, 15–30° moderate, and greater than 30° severe, although interpretation depends on the exact measurement method and clinical context.

Imaging for Tarsal Coalition

Oblique Radiographs

An oblique foot radiograph may demonstrate a calcaneonavicular coalition.

CT

CT is particularly useful for defining a talocalcaneal coalition, determining its extent, and assessing associated degenerative change.

Arthritis

Cross-sectional imaging can also assess the degree of subtalar, hindfoot, or midfoot arthritis.

Imaging for Charcot Arthropathy

Radiographs should be evaluated for fragmentation, collapse, subluxation, sclerosis, and resorption, all of which may indicate Charcot neuroarthropathy.

MRI

MRI is useful for evaluating posterior tibial tendon degeneration, tenosynovitis, partial tearing, or rupture.

It can also assess associated ligament and soft-tissue pathology.

Pathological Findings

Charcot Neuroarthropathy

Pathologic changes include bone fragmentation, fracture, resorption, and progressive joint collapse.

Posterior Tibial Tendon Dysfunction

The tendon may demonstrate degeneration, thickening, attenuation, tenosynovitis, or tearing.

Tarsal Coalition

A coalition may consist of fibrous, fibrocartilaginous, or osseous tissue between adjacent tarsal bones.

Differential Diagnosis

Pediatric Flatfoot

Important pediatric causes include benign flexible flatfoot, tarsal coalition, congenital vertical or oblique talus, and accessory navicular.

Adult-Acquired Flatfoot

In adults, the differential diagnosis includes posterior tibial tendon dysfunction or rupture, midfoot arthritis, Charcot neuroarthropathy, and neuromuscular disease.

Treatment

General Principles

Asymptomatic flatfoot does not require treatment.

Education and reassurance are appropriate, particularly in children with benign flexible flatfoot.

Treatment is directed toward symptoms and the underlying cause rather than the appearance of the foot alone.

Pediatric Flexible Flatfoot

Asymptomatic Children

No treatment is necessary when the child has painless, flexible flatfoot with normal function.

Activity-Related Pain

If symptoms occur with activity, supportive shoes may be helpful.

A prefabricated or custom medial arch support can be considered for comfort.

Orthoses

Orthotic devices may reduce symptoms in some children, but they do not reliably create a permanent arch or alter the natural structural development of the foot.

Evidence supporting routine use in asymptomatic children is limited.

Tarsal Coalition

Initial treatment of a symptomatic coalition may include rest, temporary activity restriction, NSAIDs, and immobilization in a below-knee cast or walking boot.

Immobilization

Short-term immobilization may substantially reduce pain by limiting motion across the symptomatic coalition.

Tight Achilles Tendon

Flatfoot associated with a tight heel cord may improve symptomatically with Achilles and gastrocnemius stretching.

Physical therapy can assist with a structured stretching program.

Adult-Acquired Flatfoot From Posterior Tibial Tendon Dysfunction

Initial treatment may include rest, NSAIDs, temporary immobilization, orthotic support, bracing, and weight reduction when appropriate.

Immobilization

An acute painful episode may be treated with a below-knee cast or walking boot to reduce tendon loading.

Long-Term Support

Custom arch supports or an ankle-foot orthosis may help control hindfoot valgus and support the medial arch.

Corticosteroid Injection

Direct corticosteroid injection into the posterior tibial tendon is generally avoided because of concern for tendon weakening or rupture.

Midfoot Arthritis

Treatment may include orthotic arch support, NSAIDs, footwear modification, rocker-bottom soles, stiff or steel-shank shoes, and selected intra-articular corticosteroid injections.

Charcot Arthropathy

Acute Phase

Acute Charcot neuroarthropathy requires off-loading and immobilization, commonly with a total-contact cast or equivalent protective device.

Weight bearing may need to be restricted depending on severity.

Long-Term Management

After the acute inflammatory phase settles, custom orthoses, bracing, and protective footwear may be required.

Surgery is reserved for severe deformity, instability, recurrent ulceration, or failure of nonoperative treatment.

Physical Therapy

Physical therapy can improve ankle and foot mobility, strength, gait, and Achilles flexibility.

It is particularly useful when heel-cord tightness contributes to symptoms.

Orthotic Services

An orthotist may fabricate custom arch supports or braces when more substantial mechanical control is needed.

Medication

NSAIDs may be useful when pain and swelling are significant.

They are particularly helpful during episodes of posterior tibial tendinitis, arthritis, or other inflammatory symptoms.

Surgery

Surgery is rarely required for uncomplicated flexible flatfoot.

It is considered when there is persistent pain despite appropriate conservative treatment, progressive deformity, instability, or rigid structural abnormality.

Surgical Planning

The choice of procedure depends on patient age, activity level, deformity flexibility, degree of arthritis, underlying cause, and medical comorbidities.

Procedures may include soft-tissue reconstruction, osteotomy, coalition resection, or arthrodesis.

Pediatric Flexible Flatfoot Surgery

When surgery is required for a symptomatic flexible deformity, treatment generally involves osteotomies designed to restore alignment, correct hindfoot valgus, and improve foot mechanics.

Soft-tissue procedures may be added when necessary.

Tarsal Coalition Surgery

Coalition Resection

A symptomatic coalition that fails conservative treatment may be resected.

Interposition of fat, muscle, or another tissue may be used to reduce the risk of reformation.

Subtalar Arthrodesis

If a talocalcaneal coalition involves a large portion of the subtalar joint, historically more than approximately 50%, or if substantial degenerative arthritis is present, subtalar fusion may be preferred over resection.

Achilles Tendon Lengthening

Persistent equinus caused by a tight Achilles tendon may require surgical lengthening.

Techniques include Z-lengthening or controlled partial tendon lengthening, depending on severity and age.

Posterior Tibial Tendon Surgery

Early Disease

In early posterior tibial tendon disease with relatively preserved tendon structure and alignment, synovectomy or debridement may occasionally be sufficient.

Flexible Deformity

Flexible adult-acquired flatfoot may require a combination of tendon transfer, calcaneal osteotomy, midfoot osteotomy, ligament reconstruction, or limited arthrodesis.

Rigid Deformity

When the deformity becomes rigid or significant arthritis is present, fusion procedures are often required.

Follow-Up

Prognosis

Most patients with flexible flatfoot do not develop progressive deformity and never require corrective surgery.

Children with asymptomatic flexible flatfoot generally have an excellent prognosis.

Adult-Acquired Flatfoot

Posterior tibial tendon dysfunction is an important exception because it may progressively worsen from a flexible deformity to a rigid arthritic flatfoot if untreated.

Complications

Most patients managed nonoperatively have little risk of major complications.

Persistent pain, worsening deformity, arthritis, callus formation, and reduced mobility may occur when the underlying disorder progresses.

Posterior Tibial Tendon Dysfunction

Progressive tendon insufficiency may cause increasing hindfoot valgus, forefoot abduction, arch collapse, ligament failure, and eventually rigid deformity with arthritis.

Patient Monitoring

Follow-up frequency depends on the underlying cause and severity.

Symptomatic or progressive patients may be reassessed at approximately 3-month intervals initially.

Monitoring should document pain, function, arch height, hindfoot alignment, flexibility, single-leg heel-rise ability, gait, shoe wear, and progression of deformity.