Hypermobile Pes Planus (Flexible Flatfoot)
Key Points
- Most common pediatric foot condition (10-23% of population)
- Physiological in children under 6 years
- Characterized by loss of medial longitudinal arch during weight-bearing
- Usually asymptomatic and self-limiting
- Treatment mainly required for symptomatic cases
Definition
Hypermobile pes planus is characterized by flattening of the medial longitudinal arch during weight-bearing, with restoration of the arch when non-weight-bearing or standing on tiptoes. The condition involves ligamentous laxity and is typically bilateral.
Associated Syndromes & Conditions
- Ehlers-Danlos Syndrome
- Generalized joint hypermobility
- Skin hyperextensibility
- Higher risk of chronic pain
- Marfan Syndrome
- Associated with aortic root dilation
- Tall stature and long extremities
- Lens dislocation
- Down Syndrome
- Increased ligamentous laxity
- Higher prevalence of severe flatfoot
- Cerebral Palsy
- Often associated with spasticity
- May require more aggressive management
Pathophysiology
- Primary factors:
- Ligamentous laxity
- Developmental absence of arch
- Muscular weakness
- Secondary contributors:
- Obesity
- Tight Achilles tendon
- Accessory navicular bone
Clinical Features
Symptoms
- Often asymptomatic
- When symptomatic:
- Fatigue pain in feet, ankles, or legs
- Activity-related discomfort
- Early shoe wear along inner border
- Difficulty with prolonged standing/walking
Physical Examination
- Standing examination:
- Too many toes sign
- Heel valgus > 10 degrees
- Collapsed medial longitudinal arch
- Dynamic assessment:
- Restoration of arch with toe-standing
- Jack's test (dorsiflexion of great toe)
- Heel-rise test
- Range of motion:
- Ankle dorsiflexion
- Subtalar joint motion
- Midfoot flexibility
Diagnosis & Assessment
Clinical Tests
- Jack's Test
- Dorsiflexion of hallux
- Positive: arch formation
- Indicates flexibility
- Heel Rise Test
- Observe heel inversion
- Arch formation on toe-standing
- Beighton Score
- Assessment of generalized hypermobility
- Score ≥ 4 indicates hypermobility
Imaging
- Weight-bearing radiographs:
- AP, lateral, and oblique views
- Talar-first metatarsal angle
- Calcaneal pitch angle
- Talonavicular coverage angle
- Additional imaging:
- Stress radiographs
- CT/MRI (rarely needed)
Management Approach
Conservative Treatment
- Observation
- Primary approach for asymptomatic cases
- Regular monitoring until skeletal maturity
- Physical Therapy
- Arch strengthening exercises
- Tibialis posterior strengthening
- Balance training
- Proprioception exercises
- Orthotic Devices
- Custom orthoses for symptomatic cases
- UCBL orthosis for severe cases
- Supportive footwear
Surgical Management
- Indications:
- Failed conservative treatment
- Persistent pain
- Progressive deformity
- Significant functional limitation
- Procedures:
- Calcaneal lengthening osteotomy
- Subtalar arthroereisis
- Medial soft tissue reconstruction
- Triple arthrodesis (rarely in children)
