Flat foot (pes planus) - Symptoms, Causes, Treatment & Prevention

Overview

Flat foot, also called pes planus or fallen arch, is a condition in which the arch of the foot collapses, causing the entire sole to touch the ground when standing. The condition can be flexible (arch appears when the foot is lifted) or rigid (arch is absent even when the foot is off the ground).

Flat foot occurs in 10–25 % of the general population, with higher rates in children and in adults who are overweight or have certain systemic diseases.¹ While many people remain asymptomatic, others develop pain, fatigue, or problems further up the kinetic chain (ankle, knee, hip, lower back).

Both sexes are equally affected, but prevalence differs by age:

• Infants and toddlers: almost universal (soft, pliable arches).
• Children (5–12 y): up to 30 % retain flexible flat foot.
• Adults: 10–15 % have a persistent flat arch; the rate climbs to >25 % in people with obesity or rheumatoid arthritis.

Symptoms

Symptoms range from none at all to significant discomfort. Common presentations include:

Pain

• Heel pain – often described as a dull ache behind the heel, especially after prolonged standing or walking.
• Arch pain – aching, burning, or stabbing sensations along the medial (inner) arch.
• Midfoot or forefoot pain – due to altered load distribution.
• Posterior tibial tendon pain – a sign that the supporting tendon is over‑worked.

Functional complaints

• Feet that tire quickly during activity.
• Feeling “unstable” or “wobbly” on uneven surfaces.
• Frequent tripping or a sensation of the foot “slipping” outward.
• Difficulty fitting into standard shoes; shoes may feel tight across the top of the foot.

Visible changes

• Noticeable flattening of the arch when standing.
• Overpronation – the foot rolls inward excessively during gait.
• Visible wear pattern on shoes (excessive wear on the inner side).

Secondary symptoms

• Knee, hip, or lower‑back pain linked to altered biomechanics.
• Plantar fasciitis – inflammation of the tissue that runs along the bottom of the foot.

Causes and Risk Factors

Flat foot can be congenital (present at birth) or acquired later in life.

Congenital / Developmental

• Genetic predisposition to low‑arched foot structure.
• Connective‑tissue disorders (e.g., Ehlers‑Danlos syndrome) that make ligaments lax.
• Neuromuscular conditions such as cerebral palsy or muscular dystrophy.

Acquired

• Posterior tibial tendon dysfunction (PTTD) – the tendon that supports the arch weakens, often after repetitive stress.
• Obesity – excess weight increases load on the arch.
• Trauma – fractures or sprains that damage arch‑supporting bones or ligaments.
• Arthritic conditions – rheumatoid arthritis or osteoarthritis can erode joint structures.
• Pregnancy – hormonal changes (relaxin) increase ligament laxity.
• Improper footwear – prolonged use of high‑heels, flip‑flops, or shoes lacking arch support.

Risk Factors

• Age > 40 years (degenerative changes)
• Body mass index (BMI) > 30 kg/m²
• Family history of flat foot
• Jobs requiring prolonged standing or heavy lifting
• Systemic diseases: diabetes, gout, inflammatory arthritis

Diagnosis

Diagnosis is usually clinical, supported by imaging when needed.

Physical examination

• Observation of the foot in standing and sitting positions.
• “Wet test” – patient steps on a piece of paper; a complete imprint suggests flat foot.
• Assessment of arch height, range of motion, and tenderness.
• Gait analysis to detect overpronation.

Imaging studies

• Weight‑bearing X‑rays (AP, lateral, and oblique) – evaluate bone alignment and joint space.
• Ultrasound – visualizes posterior tibial tendon integrity.
• MRI – reserved for complex cases, trauma, or when soft‑tissue pathology is suspected.

Special tests

• Flexibility assessment: arch reappears when the patient stands on tip‑toes (flexible) vs. remains flat (rigid).
• Strength testing of the intrinsic foot muscles and tibialis posterior.

Treatment Options

Treatment is tailored to severity, symptoms, and patient goals. The majority of cases improve with conservative measures.

Non‑pharmacologic measures

• Foot orthoses – custom‑made or over‑the‑counter arch supports to redistribute pressure.
• Appropriate footwear – firm heel counter, cushioned sole, and built‑in arch.
• Physical therapy – strengthening (tibialis posterior, intrinsic foot muscles) and stretching (Achilles, calf). Example exercises: towel curls, marble pick‑ups, heel raises.
• Weight management – reducing excess weight lessens mechanical load.
• Activity modification – low‑impact exercises (swimming, cycling) while avoiding prolonged standing on hard surfaces.

Medications

• Non‑steroidal anti‑inflammatory drugs (NSAIDs) such as ibuprofen or naproxen for pain and inflammation (short‑term use).
• Topical NSAIDs or analgesic creams for focal heel pain.
• In cases of tendonitis, a short course of oral corticosteroids may be considered under physician supervision.

Procedural / Surgical options

Reserved for rigid flat foot, persistent pain despite 6–12 months of conservative care, or severe deformity.

• Triple‑bone osteotomy – realigns the rearfoot and midfoot.
• Subtalar arthroereisis – implants (e.g., calcium sulfate) limit excessive pronation.
• Tendon transfers or reconstruction – especially for posterior tibial tendon dysfunction.
• Fusion (arthrodesis) – joins joints to create a stable, albeit less mobile, foot.
• All procedures are typically followed by a period of immobilization and structured rehabilitation.

Adjunct therapies

• Ice packs (15‑20 min) after activity to reduce inflammation.
• Night splints for severe tendon stretching in PTTD.

Living with Flat Foot (Pes Planus)

Effective self‑management can keep symptoms under control and prevent progression.

Daily habits

• Choose shoes with built‑in arch support; replace them every 6–12 months.
• Insert custom or over‑the‑counter orthotic insoles if recommended by a podiatrist.
• Perform foot‑strengthening exercises at least 3 times per week (e.g., short foot exercise, toe yoga).
• Stretch calf and Achilles tendons daily, especially after activity.
• Maintain a healthy weight; aim for a BMI < 25 kg/m² if possible.
• Limit time spent standing on hard surfaces; use anti‑fatigue mats at work.

Travel tips

• Carry orthotic inserts and a pair of supportive shoes in your luggage.
• Take short walks and stretch every hour on long flights or car trips.

When to follow‑up

If pain worsens despite conservative treatment, or if you develop new swelling, instability, or numbness, schedule a review within 4–6 weeks.

Prevention

• Encourage children to wear supportive shoes during early walking years; avoid prolonged barefoot walking on hard surfaces.
• Strengthen foot muscles early through play (e.g., picking up objects with toes).
• Maintain a balanced diet and regular exercise to avoid obesity.
• Use proper technique and supportive footwear for sports that involve running or jumping.
• For adults with known risk factors (obesity, rheumatoid arthritis), routine foot exams can catch early changes.

Complications

If left untreated, flat foot can lead to:

• Chronic posterior tibial tendon dysfunction → rigid flat foot.
• Plantar fasciitis or heel spurs.
• Accelerated wear of the ankle and knee joints, increasing risk of osteoarthritis.
• Altered gait causing lower‑back pain or sacroiliac joint strain.
• In rare cases, stress fractures of the navicular or metatarsals due to abnormal load distribution.

When to Seek Emergency Care

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References:

1. Mayo Clinic. “Flatfoot (pes planus).” Accessed May 2026.
2. American Orthopaedic Foot & Ankle Society. “Epidemiology of flatfoot.” J Bone Joint Surg Am. 2020;102(12):1065‑1072.
3. National Institute of Arthritis and Musculoskeletal and Skin Diseases. “Posterior tibial tendon dysfunction.” 2023.
4. CDC. “Obesity and musculoskeletal health.” 2022.
5. Cleveland Clinic. “Flatfoot treatment options.” 2024.