Pes planus

Pes planus (flatfoot) is a type of foot deformity characterized by the absence or reduction of the medial longitudinal arch while standing. Pes planus can be rigid or functional. In rigid pes planus, the arch is absent regardless of foot position, while in functional pes planus, the medial arch is visible when sitting or standing on tiptoes. Rigid pes planus is rare and may be congenital or acquired. Functional pes planus is the most common type and is typically a painless, normal physiological variant that resolves by adolescence. Functional pes planus is typically diagnosed clinically and rarely requires further evaluation. Referral to an orthopedic surgeon should be considered for patients with pain or limited function.

This article covers functional pes planus; see “Subtypes and variants” for rigid pes planus and acquired pes planus.

• Occurs in > 95% of children ≤ 2 years of age ^[1]
• Prevalence decreases with age: seen in < 20% of adults ^[1][2]

Epidemiological data refers to the US, unless otherwise specified.

• Generalized ligament laxity
• Muscle weakness
• Contracture of the gastrocnemius-soleus muscles (rare)

Symptoms

• Most patients are asymptomatic.
• Occasional arch pain after excessive exercise (e.g., long walks)
• Patients may present with complications of pes planus.

Examination

• With the patient standing, common findings include:
  • Hindfoot valgus deformity ^[2]
  • Midfoot position is dorsiflexed and abducted
  • Forefoot is pronated or externally rotated
  • Flattening of the medial arch
• Calluses may form on the plantar surface of the midfoot.
• Patients have a full range of motion.

Rigid pes planus ^[2]

• Definition: a form of pes planus where the medial arch remains flattened, regardless of foot positioning
• Etiology
  • Congenital
  • Acquired
    • Trauma
    • Infection
    • Arthritis
    • Neuromuscular disease
• Diagnostics
  • Perform initial diagnostics for functional pes planus.
  • Choice of further diagnostics, including imaging, depends on suspected underlying etiology.
• Treatment
  • Treat the underlying cause.
  • Further management depends on symptoms and can include orthotics and surgery.

Congenital rigid pes planus ^[3]

• Definition: rare, complex foot deformity with a fixed vertical position of the talus and luxation of the talocalcaneonavicular joint
• Etiology
  • Can be inherited in an autosomal dominant pattern ^[3]
  • Associated with neurological and/or genetic disorders
• Pathogenesis
  • Cranial luxation of the navicular bone
  • (Sub)luxation of the talonavicular joint and the subtalar joint
  • Short Achilles tendon
• Clinical features
  • Convex plantar surface
  • Abduction, pronation, and dorsal extension of the forefoot
• Diagnostics ^[3]
  • Foot examination
    • Head of the talus: palpable to touch
    • Medial longitudinal arch: stiff and flat with standing and sitting; no change with tiptoe standing ^[2]
  • Comprehensive neurological examination to rule out comorbid conditions ^[3]
  • X-ray foot: Axes of the tibia and talus appear parallel on the lateral image.
• Treatment: Refer to an orthopedic surgeon for management. ^[2][3]
  • Serial casting of the newborn's limb: to restore anatomical foot alignment to optimize weight distribution
  • Surgery (e.g., open reduction): often performed before 3 years of age in patients with abnormal bony fusion (e.g., tarsal coalition) ^[2]

Acquired pes planus ^[4]

• Definition
  • A foot deformity characterized by the collapse of the longitudinal arch, usually due to posterior tibialis tendon insufficiency that manifests as a flat or convex plantar surface of the foot
  • Maybe cause functional or rigid pes planus
• Risk factors
  • Preexisting foot pathology (e.g., posterior tibial tendon dysfunction)
  • Repetitive high-impact activities (e.g., running, soccer)
  • Trauma
  • Obesity
  • Systemic diseases (e.g., diabetes, autoimmune arthritis)
  • Steroid use
• Diagnostics
  • Similar to diagnostics for functional pes planus
  • Weight-bearing imaging (e.g., x-ray, CT, or MRI) confirms the diagnosis and is helpful to:
    • Rule out other foot deformities
    • Evaluate for arthritis
    • Assess the severity of the foot deformity for surgical planning
• Treatment
  • Recommend temporary rest with activity modification and use of NSAIDs as needed.
  • If there is minimal improvement, refer to an orthopedic specialist for management, including:
    • Orthotics
    • Physical therapy
    • Surgery

General principles ^[1]

• Functional pes planus is a clinical diagnosis.
• Examination findings can help:
  • Distinguish between functional pes planus and rigid pes planus
  • Determine underlying etiology
• Imaging is not usually required, consider x-ray foot in diagnostic uncertainty. ^[5]

Do not perform routine imaging to diagnose asymptomatic functional pes planus. ^[5]

Confirmatory examination findings ^[1][2]

• “Too many toes” sign
  • Observe the patient from behind while they stand or walk.
  • Characteristic finding: Toes in addition to the fifth and half of the fourth toe are seen.
• Medial arch position: can help differentiate between rigid and functional pes planus
  • Functional pes planus
    • Medial arch disappears when standing
    • Medial arch becomes visible again with dorsiflexion of the great toe while standing (also known as the “toe raising test”) or with tiptoe standing
    • In mild deformity, the arch may be visible on standing; standing on one foot may reveal arch collapse.
  • Rigid pes planus: the medial arch does not change with position

Assessment for underlying etiology ^[1][2]

• Beighton score: for underlying hypermobiltiy
• Torsional profile: for angular and/or rotational deformities
• Silfverskjöld test: for isolated gastrocnemius contracture

• Asymptomatic individuals
  • Treatment is not required unless symptoms develop. ^[1][6]
  • Offer reassurance that functional pes planus usually resolves by adolescence without intervention. ^[1]
• For patients with pain or reduced function: ^[1][6]
  • Offer conservative treatment.
    • Rest with activity modification, ice, and massage
    • NSAIDs (see “Oral analgesics” for dosages)
    • Physical therapy: especially for patients with a tight Achilles tendon ^[2]
    • Consider referral to podiatry for therapeutic footwear (e.g., custom orthotics, heel wedges). ^[1][2]
  • If there is minimal improvement:
    • Consider alternative diagnoses (e.g., congenital rigid pes planus, Achilles tendon contracture).
    • Refer to an orthopedic specialist for surgical evaluation.

Custom orthotics or shoe inserts are not recommended for patients with asymptomatic, or minimally symptomatic, pes planus. ^[6]

• Tarsal tunnel syndrome ^[7]
• Sinus tarsi syndrome ^[1]
• Recurrent ankle sprains ^[1]

We list the most important complications. The selection is not exhaustive.