Can Pes Planus Cause Plantar Fasciitis or Plantar Plate Rupture/Dislocation?
Yes, pes planus (flat foot) is a recognized causative factor for plantar fasciitis, with evidence showing a significantly higher incidence in flat-footed individuals, but the relationship with plantar plate rupture/dislocation is less established and appears to be primarily trauma-related rather than directly caused by the flat foot deformity itself.
Pes Planus and Plantar Fasciitis
The evidence strongly supports a causal relationship between pes planus and plantar fasciitis:
Incidence data: Research demonstrates that 43.4% of patients with flexible flatfoot develop plantar fasciitis compared to only 8.7% in those with normal arches 1. This represents a roughly 5-fold increased risk.
Structural changes: Ultrasound studies reveal that individuals with pes planus have significantly thinner plantar fascia in the middle (-10.6%) and anterior (-21.7%) portions, along with altered intrinsic foot muscle architecture 2. The extrinsic muscles (flexor digitorum longus and flexor hallucis longus) show compensatory hypertrophy (24-28% larger), suggesting they work harder to support the collapsed medial longitudinal arch.
Biomechanical mechanism: Pes planus creates excessive tensile strain within the plantar fascia due to the lowered medial longitudinal arch 3, 4. The anatomical deformity combined with excessive pronation of the subtalar joint generates repetitive microtrauma to the fascial enthesis.
Clinical Recognition
The American College of Foot and Ankle Surgeons guidelines specifically recommend avoiding flat shoes and barefoot walking in heel pain management 5. This recommendation implicitly acknowledges that flat foot mechanics contribute to plantar fasciitis development. Treatment protocols include arch supports and custom orthotics to correct the biomechanical abnormality 6.
Important Caveat
While the association is clear, the pathophysiology may be more complex than simple tensile overload. Histological studies rarely show inflammation in chronic plantar fasciitis, suggesting alternative mechanisms like stress-shielding, vascular disturbances, or metabolic factors may also contribute 4.
Pes Planus and Plantar Plate Rupture/Dislocation
The relationship here is much weaker and primarily indirect:
Trauma-dominant etiology: Plantar plate ruptures typically result from acute hyperextension injuries with axial loading forces 7. The case literature describes these injuries occurring during sports activities (gymnastics, basketball) rather than as chronic degenerative consequences of foot structure 8, 7.
Lack of direct evidence: None of the available guidelines or research studies establish pes planus as a causative factor for plantar plate pathology. The subtalar joint dislocation case in an athlete with pes planus 8 represents a traumatic injury where the flat foot may have been an incidental finding rather than a causative factor.
Biomechanical considerations: While pes planus alters forefoot loading patterns—with symptomatic individuals showing lateralized pressure distribution 9—this does not translate into documented increased risk of plantar plate failure. The plantar plate primarily resists hyperextension forces at the metatarsophalangeal joints, a mechanism distinct from the arch collapse seen in flat feet.
Clinical Implications
For plantar fasciitis prevention in pes planus patients:
- Prescribe custom-made insoles or extra-depth shoes with arch support 10
- Implement calf-muscle stretching and foot-ankle exercise programs 5, 6
- Avoid barefoot walking and thin-soled footwear 10, 5
- Consider heel lifts to unload the plantar fascia 6
For plantar plate injuries:
- Recognize these as primarily traumatic rather than degenerative
- Maintain high clinical suspicion in patients with great toe hyperextension injuries
- Understand that pes planus is not a documented risk factor requiring specific preventive measures for plantar plate pathology
The key distinction is that pes planus creates chronic biomechanical stress leading to plantar fasciitis through repetitive microtrauma, whereas plantar plate injuries require acute traumatic forces that are not inherently related to foot arch structure.