What Causes Plantar Fasciitis
Plantar fasciitis results from repetitive stress and degenerative changes at the origin of the plantar fascia on the medial tubercle of the calcaneus, not primarily from inflammation despite its name 1, 2.
Primary Pathophysiology
The condition develops through a degenerative process rather than an inflammatory one, occurring at the fascial insertion point on the heel bone 3. This repetitive microtrauma leads to collagen breakdown and structural changes in the plantar fascia tissue 1, 2.
Key Risk Factors (Evidence-Based)
The strongest evidence identifies three independent risk factors that significantly increase plantar fasciitis risk 4:
1. Limited Ankle Dorsiflexion (Most Important)
- Individuals with ≤0 degrees of dorsiflexion have a 23-fold increased risk (odds ratio 23.3) compared to those with >10 degrees 4
- Often associated with gastrocnemius (calf muscle) tightness 2
- This is the single most important modifiable risk factor
2. Obesity
- Body mass index >30 kg/m² carries a 5.6-fold increased risk compared to BMI ≤25 kg/m² 4
- Excess weight increases mechanical stress on the plantar fascia 5
3. Prolonged Weight-Bearing
- Spending the majority of workday on feet increases risk 3.6-fold 4
- Excessive standing or running creates cumulative microtrauma 5
Additional Contributing Factors
Beyond the three primary risk factors, other biomechanical abnormalities contribute 5, 3:
- Excessive foot pronation (flat feet/pes planus)
- High arches (pes cavus)
- Middle age (most common presentation)
- Affects both sedentary and athletic populations equally 5
Clinical Pitfall to Avoid
Do not assume plantar fasciitis is purely inflammatory—the pathology is degenerative 3. This distinction matters because it explains why anti-inflammatory treatments alone often fail and why the condition typically requires 3-6 months to resolve even with appropriate treatment 2. The term "fasciitis" is actually a misnomer; "fasciosis" would be more accurate given the degenerative nature.
The combination of these factors—particularly tight calf muscles limiting ankle motion, excess body weight, and repetitive loading—creates the mechanical overload that drives the degenerative process in the plantar fascia 4.