What is Pes Planus?
Pes planus, also known as flatfoot or pes planovalgus, is a foot deformity characterized by a reduction or complete absence of the medial longitudinal arch of the foot, resulting in the entire sole contacting the ground during weight-bearing. 1
Clinical Classification
Pes planus exists in two distinct forms that require different management approaches:
Flexible Pes Planus
- The arch appears normal during non-weight-bearing activities or when standing on tiptoes, but flattens when standing with full weight 2
- This is the most common type, affecting up to 14% of children and up to 25% of the total population in at least one foot 3
- Often part of normal developmental variation in children, typically resolving as foot musculature strengthens with age 2
- Represents 94.2% of pes planus cases in some populations 4
Rigid Pes Planus
- The arch remains stiff and collapsed regardless of weight-bearing status 2
- Represents only 5.8% of cases 4
- Requires immediate referral to a subspecialist for evaluation and treatment 2
Clinical Significance
Biomechanical Impact
Pes planus causes several functional consequences:
- Increased plantar pressures in the midfoot during walking and standing 5, which can lead to ulceration in patients with neuropathy
- Altered foot biomechanics affecting the entire lower limb 6
- Compensatory pronation, one of the most common lower extremity disorders in sports medicine 6
- Potential changes in neurosensory mechanisms including proprioception and balance 7
Associated Conditions
The deformity is recognized as a significant foot deformity in multiple clinical contexts 1:
- Listed alongside hammer toes, claw toes, hallux valgus, prominent metatarsal heads, and pes cavus
- Can result from Charcot neuro-osteoarthropathy, trauma, amputations, or other foot surgery
- May be associated with rheumatologic, neuromuscular, genetic, or collagen conditions 2
Etiology
Pediatric Pes Planus
- Often congenital, typically resolving with age 2
- May persist into adulthood in approximately 25% of the population 3
Adult-Acquired Pes Planus
The most common cause in adults is posterior tibial tendon dysfunction 2, though several other etiologies exist.
Clinical Evaluation
Assessment should identify:
- Presence of arch during non-weight-bearing versus weight-bearing to distinguish flexible from rigid types 2
- Associated foot deformities (hammer toes, limited joint mobility)
- Signs of underlying systemic conditions (rheumatologic, neuromuscular, genetic, or collagen disorders) 2
- In diabetic patients: presence of neuropathy and vascular status, as pes planus increases ulceration risk 5
Common Pitfalls
- Do not assume all pes planus causes overpronation—recent evidence shows lateral displacement of the center of pressure in the forefoot can occur 4
- Do not overlook rigid pes planus—this requires subspecialist referral, not conservative management 2
- In diabetic patients with pes planus and neuropathy, the deformity significantly increases midfoot ulceration risk due to elevated plantar pressures that go unperceived 5