What is the approach to evaluating a patient with flat feet (pes planus) on physical exam, considering their medical history, age, and overall health status?

Physical Examination of Flat Feet (Pes Planus)

Begin by determining if the flatfoot is flexible (physiologic) or rigid (pathologic) using the weight-bearing versus non-weight-bearing arch assessment, as this distinction drives all subsequent management decisions. 1

Initial Classification: Flexible vs. Rigid

• Flexible flatfoot: The longitudinal arch is present when the foot is off the ground (open kinetic chain) but disappears with weight-bearing (closed kinetic chain). 1
• Rigid flatfoot: The longitudinal arch is absent both with and without weight-bearing, indicating pathologic changes. 1
• This distinction is the critical first step, as flexible flatfoot may be part of normal development in children, while rigid flatfoot requires investigation for underlying pathology. 1, 2

Systematic Physical Examination Components

Visual Inspection (Standing Position)

• Observe the medial longitudinal arch height from both medial and posterior views while the patient stands with feet shoulder-width apart. 3
• Assess for hindfoot valgus by viewing from behind—look for excessive heel eversion and the "too many toes sign" (more than 1-2 toes visible lateral to the heel when viewing from behind). 4
• Check for forefoot abduction: The forefoot may appear to point outward relative to the hindfoot. 1
• Inspect skin integrity for ulcerations, calluses, areas of hyperemia, or breaks in skin, particularly over pressure points. 5, 6

Dynamic Assessment

• Single-leg heel raise test: Ask the patient to stand on one leg and rise onto the toes. In a flexible flatfoot with intact tibialis posterior function, the heel should invert and the arch should reconstitute. Inability to perform this test or failure of the heel to invert suggests tibialis posterior dysfunction or rigid deformity. 4
• Jack's test (windlass mechanism): With the patient standing, passively dorsiflex the great toe. A normal response shows reconstitution of the medial arch; absence suggests rigid flatfoot or midfoot instability. 3

Palpation and Range of Motion

• Palpate the tibialis posterior tendon along its course from behind the medial malleolus to its insertion on the navicular, assessing for tenderness, swelling, or discontinuity. 4
• Assess subtalar joint motion: With the patient seated and ankle in neutral, grasp the heel and assess inversion/eversion range. Restricted motion suggests tarsal coalition or arthritic changes. 7
• Evaluate ankle dorsiflexion with knee extended and flexed to assess for Achilles tendon contracture (equinus), which is a major contributing factor to flatfoot deformity. 1, 7
• Palpate for tenderness over the talonavicular joint, spring ligament complex, and sinus tarsi. 4

Assessment for Contributing Risk Factors

• Test for ligamentous laxity: Assess Beighton score (thumb to forearm, fifth finger hyperextension >90°, elbow/knee hyperextension, forward trunk flexion with palms flat). Generalized ligamentous laxity predisposes to flatfoot progression. 1
• Evaluate for rotational deformities: Assess femoral anteversion (hip internal/external rotation range in prone position) and tibial torsion (thigh-foot angle), as these alter ground reaction forces on the foot. 1
• Check for tibial varum (bowleg deformity), which increases medial loading and flatfoot tendency. 1
• Palpate for os tibiale externum (accessory navicular), a bony prominence at the navicular tuberosity that can cause pain and contribute to arch collapse. 1

Neurovascular Assessment

• Perform 10-g monofilament testing at plantar sites (hallux, first/third/fifth metatarsal heads) plus at least one additional neurological test (pinprick, vibration with 128-Hz tuning fork, temperature perception, or ankle reflexes) to assess for loss of protective sensation. 5, 6, 8
• Palpate dorsalis pedis and posterior tibial pulses bilaterally and grade as 0 (absent), 1 (diminished), 2 (normal), or 3 (bounding). 5, 6, 9
• Assess capillary refill time, rubor on dependency, pallor on elevation, and venous filling time if vascular compromise is suspected. 5, 6

Assessment for Foot Deformities

• Identify structural deformities including bunions (hallux valgus), hammertoes, prominent metatarsal heads, and Charcot arthropathy, as these increase plantar pressures and ulceration risk. 5, 8
• Document any prior ulcerations, amputations, or Charcot foot history. 6, 8

Common Pitfalls to Avoid

• Do not assume all flatfeet require treatment: Up to 25% of adults have deficient medial longitudinal arch without symptoms, and flexible flatfoot in children often resolves with normal development. 2
• Do not rely solely on visual inspection: The single-leg heel raise test is essential to differentiate flexible from rigid deformity and assess tibialis posterior function. 4
• Do not overlook equinus: Achilles tendon contracture is a major modifiable risk factor that must be assessed with knee extended and flexed. 1, 7
• Do not forget to assess overall lower extremity alignment: Rotational deformities and tibial varum significantly impact flatfoot biomechanics and must be corrected for optimal outcomes. 1, 7