What are the diagnostic criteria for pes planus (flat foot)?

From the Guidelines

The diagnostic criteria for pes planus (flat foot) include both clinical and radiographic findings, with clinical characteristics such as a collapsed medial longitudinal arch, excessive pronation, and heel valgus being key indicators 1. The diagnosis of pes planus involves a combination of clinical observation and radiographic evaluation. Clinically, flat foot is characterized by a medial longitudinal arch that collapses during weight-bearing, resulting in the entire sole of the foot contacting the ground.

• Key clinical findings include:
  • Excessive pronation
  • Heel valgus (outward turning of the heel)
  • Forefoot abduction
  • Medial bulging of the talonavicular joint
  • The "too many toes" sign, where more than the normal number of toes are visible when viewing the foot from behind, indicates hindfoot valgus
• Radiographic criteria include measuring angles on weight-bearing X-rays, such as the talocalcaneal angle (>30° indicates flat foot), talonavicular coverage angle, and calcaneal pitch angle (<18° suggests flat foot) 1.
• Flat foot may be flexible (arch appears when non-weight-bearing or standing on tiptoes) or rigid (arch remains flat in all positions).
• Additional assessment should include evaluation of Achilles tendon tightness, hindfoot mobility, and neuromuscular function, as these factors influence treatment decisions.
• Pes planus or planovalgus is seen in two-thirds of individuals with cardio-facio-cutaneous syndrome and tends to be more severe than in the general population, with significant forefoot valgus 1.
• Treatment is generally nonsurgical; however, those with severe deformity and/or significant functional impairment may require surgical correction.
• It is essential to note that pes planus exists on a spectrum from asymptomatic to severely disabling, with treatment determined by symptom severity rather than appearance alone.

From the Research

Diagnostic Criteria for Pes Planus

The diagnostic criteria for pes planus, also known as flat foot, can be summarized as follows:

• Flexible pes planus is defined as a normal arch during non-weight-bearing activity or tiptoeing, with a flattening arch on standing 2
• Rigid pes planus is characterized by a stiff and collapsed arch with or without weight bearing 2
• Pes planus can be diagnosed through clinical and x-ray evaluation, which can assist in staging the condition and guiding treatment decisions 2

Key Characteristics

Some key characteristics of pes planus include:

• Forefoot abduction
• Collapse of the medial longitudinal arch
• Hindfoot valgus 3
• Increased calcaneal offset index (COI) in pes planus (hindfoot valgus) 3
• Flat midfoot/forefoot and hindfoot varus in pes planovarus 4

Radiographic Measurements

Radiographic measurements can be used to assess the degree of hindfoot alignment in patients with pes planus, including:

• Anteroposterior talocalcaneal angle (Kite's)
• Calcaneal pitch angle (CPA)
• Calcaneal offset index (COI) 3
• Talometatarsal-1 angle lateral (TMT1lat) and dorsoplantar (TMT1dp)
• Talocalcaneal angle lateral (TCAlat) and dorsoplantar (TCAdp) 4

Treatment

Treatment for pes planus depends on the severity and symptoms of the condition, and may include:

• Conservative treatment, such as orthotics and physical therapy 5
• Surgical intervention, such as Achilles tendon lengthening, bone-cutting procedures, fusion of joints, or insertion of a silicone or metal cap into the sinus tarsi 5, 6