Flat Feet

What “flat feet” actually means — and why it matters which kind you have

“Flat feet” is one of the most misunderstood foot conditions I see. Patients walk in convinced their flat arches are the cause of every ache they’ve ever had — and then there are patients who have full-blown posterior tibial tendon dysfunction and don’t know it because they think “flat feet are normal in my family.”

The first thing I do when someone comes in with arch concerns is figure out which of four very different conditions they actually have:

• Pediatric flexible flatfoot: Normal in kids under 6. Most resolve. Treat only if painful or persists past 10.
• Adult flexible flatfoot (congenital): Always had flat arches. Painless. Doesn’t progress. Usually needs nothing.
• Adult-acquired flatfoot (PTTD): Arch you used to have is now collapsing. This is the dangerous one. Progresses through stages.
• Rigid flatfoot (tarsal coalition): Arch doesn’t reform on tiptoes. Usually pediatric. Often surgical.

The reason this distinction matters: a 35-year-old with congenital flat feet who runs marathons pain-free needs zero intervention. A 50-year-old whose right arch dropped over the past 8 months and now hurts at the inner ankle is in Stage 2 PTTD — and without proper bracing and rehab, they’re heading toward Stage 3 (rigid deformity) and a much bigger surgery in a few years.

The “tiptoe test” — the single most important diagnostic for adult flat feet

Stand barefoot in front of a mirror. Try to rise up onto the ball of your foot on one leg at a time, then both. Watch what happens to the arch and the heel:

• Arch reforms, heel rotates inward: Flexible flatfoot. Either congenital (always like this) or early PTTD.
• Arch doesn’t reform, heel stays angled out: Likely Stage 3-4 PTTD or tarsal coalition. Rigid deformity — surgical territory.
• Can’t rise up at all on the affected side: Stage 2-3 PTTD. The posterior tibial tendon is failing.
• Pain at the inner ankle/arch during the attempt: Active PTTD regardless of stage. Get evaluated.

This 30-second test gives me more diagnostic information than most $400 imaging studies. If you’re over 40 and can’t do a single-leg heel rise on one side, get evaluated — that one finding alone correlates strongly with surgical-stage PTTD.

The 4 stages of PTTD — and which respond to non-surgical care

Posterior tibial tendon dysfunction (PTTD) is the most common cause of adult-acquired flatfoot. The posterior tibial tendon is the main dynamic support of your arch — when it weakens or tears, the arch collapses, the heel rotates outward, and the forefoot rotates away. Johnson and Strom’s 1989 staging system (with later modifications by Myerson) is the framework I use to set treatment expectations:

Stage 1: Tendinosis without deformity

Pain along the inner ankle and arch. Tendon is inflamed/degenerating but the arch shape is still normal. You can still do single-leg heel rises but it hurts. Non-surgical care succeeds in 80-90% of Stage 1 patients with proper orthotics, eccentric strengthening, and brief immobilization if needed.

Stage 2: Flexible deformity (most common stage at presentation)

Arch has dropped, foot looks flatter, heel has rotated outward — but the deformity is still flexible (correctable by hand and reforms when you sit). This is where most patients first show up because the cosmetic change is noticeable. Single-leg heel rise is weak or impossible. ~60-70% of Stage 2 patients improve significantly with custom orthotics + medial post + AFO bracing × 3 months. The remaining 30-40% eventually need surgical reconstruction.

Stage 3: Rigid deformity

The hindfoot is now stuck in the collapsed position — you can’t push it back to neutral by hand. Often associated with arthritis in the subtalar joint. Non-surgical care can only manage pain at this stage, not correct the deformity. Surgical reconstruction (subtalar fusion or triple arthrodesis combined with tendon reconstruction) is the definitive treatment.

Stage 4: Deformity + ankle valgus

The deformity has progressed to the ankle joint itself, with deltoid ligament failure causing the talus to tilt. This is the worst-case scenario and usually requires ankle reconstruction or fusion in addition to hindfoot reconstruction.

Non-surgical treatment — what actually works

For Stage 1-2 PTTD, congenital flexible flatfoot causing pain, and most pediatric cases, treatment is conservative. Here’s what I prescribe in actual clinic — ranked by evidence and outcome data:

Level A evidence: Custom orthotics with medial heel post

Not OTC arch supports. Not “custom” insoles from a kiosk. Genuine custom orthotics cast from a non-weight-bearing impression, with a deep heel cup, medial flange, and medial heel post (varus post). Multiple studies — including the 2006 Lin et al. RCT in Foot & Ankle International — show custom orthotics reduce PTTD pain by 60-80% and slow progression at 1-year follow-up. A 2017 systematic review confirmed orthotics as the foundation of non-surgical Stage 1-2 management.

What I look for in a properly designed PTTD orthotic: at least 4mm medial heel post, 6-8° rearfoot varus correction, deep heel cup (≥16mm), medial flange that extends up to support the navicular. Cheap OTC arch supports lack all of these features and provide essentially no biomechanical correction for true PTTD.

Level A evidence: Arizona AFO brace (Stage 2 only)

For Stage 2 patients, an Arizona-style ankle-foot orthosis (lace-up leather AFO with custom mold) worn for 3-4 months can significantly delay or prevent progression. A 2009 retrospective study of 64 patients showed 67% avoided surgery at 5-year follow-up after AFO + orthotic protocol. Less attractive than just an insole, but the structural support during the inflammation/healing phase is what allows the tendon to recover.

Level B evidence: Eccentric strengthening protocol

The posterior tibial tendon — like the Achilles — responds to controlled eccentric loading. The protocol I prescribe: resisted foot inversion (using a TheraBand) with the ankle in plantarflexion, 3 sets of 15 reps, 2x daily, for 12 weeks. Combined with single-leg heel rises (start seated, progress to standing, progress to single-leg). Kulig et al. 2009 in Physical Therapy showed a structured eccentric program significantly improved pain and function in Stage 1-2 PTTD.

Level B evidence: Short-term immobilization (boot)

For acute Stage 1-2 flares with significant inflammation, 4-6 weeks in a CAM walker boot reduces tendon load and breaks the inflammation cycle. This is what I use when patients can barely walk on the affected side. Boot off → transition into AFO + custom orthotic for the next 3 months of active rehab.

Level C evidence: PRP injections

Platelet-rich plasma into the diseased tendon under ultrasound guidance shows promise in small case series for Stage 1 tendinosis, but the data is not as robust as for plantar fasciitis or Achilles tendinopathy. I consider PRP for Stage 1 patients who’ve failed 6+ months of orthotics + eccentrics before recommending tendon debridement surgery.

What does NOT work for PTTD

• Cortisone injections into the tendon: Contraindicated. Increases rupture risk. I’ve seen completed tendon ruptures within weeks of injection.
• OTC arch supports alone: Inadequate biomechanical correction for true PTTD.
• “Strengthening the arch” with marbles or towels: Mild benefit at best. Not a substitute for properly-loaded tendon work.
• Going barefoot to “build the arch”: Actively harmful for PTTD. Accelerates collapse.

Surgical reconstruction — when conservative care isn’t enough

About 30-40% of Stage 2 PTTD patients and essentially all Stage 3-4 patients need surgical reconstruction. Modern PTTD reconstruction is a multi-component operation tailored to your specific deformity pattern. The basic building blocks:

• FDL (flexor digitorum longus) tendon transfer: Borrows your toe-flexor tendon to replace the diseased posterior tibial tendon. Standard for Stage 2-3.
• Medializing calcaneal osteotomy (MCO): Cut and shift the heel bone medially to re-create a varus moment. Restores the lever arm.
• Lateral column lengthening (Evans osteotomy): Adds a wedge to lengthen the lateral column and re-establish forefoot alignment.
• Cotton osteotomy: Plantarflex the medial cuneiform to address forefoot supination.
• Subtalar arthrodesis (fusion): Stage 3 — fuses the heel joint when arthritis is established.
• Triple arthrodesis: Stage 3-4 — fuses three hindfoot joints when multiple are arthritic.

For most Stage 2 patients I see, the typical operation is FDL transfer + medializing calcaneal osteotomy ± Cotton osteotomy, performed together. Recovery: 6 weeks non-weight-bearing in a cast or boot, then progressive weight-bearing in a boot until week 12, then transition to a normal shoe with orthotic. Most patients are back to low-impact activities at 4-6 months and full activity at 9-12 months.

Outcome data: studies of FDL transfer + MCO in Stage 2 PTTD report 85-90% patient satisfaction and significant pain reduction at 5-year follow-up. Stage 3 fusion outcomes are also good (~80-85% satisfaction) but recovery is longer and you lose hindfoot motion permanently.

Pediatric flat feet — when to worry, when to wait

Nearly every child under 4 has flat feet — the fat pad in the medial arch hasn’t resorbed and the bones haven’t finished arching. Most resolve naturally by age 6-10. The question parents always ask: “Does my kid need orthotics?”

My evaluation in 2026:

• Painless flexible flatfoot in a child under 8: Watch. No intervention needed. Most resolve.
• Flatfoot causing pain, fatigue, or tripping: Custom orthotics — typically reduces symptoms within weeks.
• Rigid flatfoot (arch doesn’t reform on tiptoes): Get imaging. Tarsal coalition is common in this presentation and may need surgical resection if symptomatic.
• Severe flexible flatfoot in a teenager with persistent pain: Consider subtalar arthroereisis (a small internal stent that limits hindfoot motion) — outpatient surgery with rapid recovery, removable if needed.

The honest truth: asymptomatic flexible flatfoot in children doesn’t need treatment. I’ve seen kids put in orthotics by well-meaning parents who didn’t need them — and these kids grow up fine without them. Save your money for the ones who genuinely have symptoms.

When to see a podiatrist — Howell & Bloomfield Hills appointments

See a podiatrist within 30 days if:

• Your arch has visibly dropped over the past 12 months
• You have pain on the inside of your ankle or under the arch
• You can’t do a single-leg heel rise on one side
• Your shoes wear unevenly on the inside
• A child has rigid flatfoot or pain with walking
• You’re a runner with newly-onset arch pain that hasn’t responded to orthotics

At Balance Foot & Ankle, our flatfoot evaluation includes a hands-on biomechanical exam, tiptoe and single-leg heel rise testing, and weight-bearing X-rays (if PTTD is suspected) to grade the deformity. We custom-fit orthotics in-office and have AFO bracing options when needed. Surgical reconstruction is performed by Dr. Tom Biernacki, DPM, FACFAS at our Howell and Bloomfield Hills locations.

Frequently asked questions

Are flat feet always a problem?

No. Painless congenital flat feet in adults rarely need any treatment. Many marathoners, athletes, and active adults have lifelong flat feet without any functional consequence. The condition becomes a problem when (1) the arch is acutely collapsing in adulthood — which signals PTTD — or (2) flat feet cause secondary pain in the arch, ankle, knees, or low back.

Will custom orthotics fix my flat feet permanently?

Orthotics support and unload the arch — they don’t restructure your foot. Worn consistently, they reduce pain and slow PTTD progression dramatically. Off them, the symptoms return because the underlying biomechanics haven’t changed. Think of them like glasses: they correct the problem while you’re using them, not after.

How is PTTD different from regular flat feet?

PTTD is an acquired condition — you had a normal arch and it’s collapsing because the posterior tibial tendon is failing. Pain at the inner ankle, progressive arch drop over months, inability to do a single-leg heel rise, and unilateral asymmetry are the classic signs. Congenital flat feet have been flat your whole life, are usually symmetric, and don’t progress.

Can I run with flat feet?

Yes — assuming they’re painless. Many elite runners have flat feet. If you’re getting pain, you may need motion-control or stability shoes plus a custom orthotic. If pain persists, get evaluated for PTTD before assuming it’s just “flat-foot running.”

Do flat feet cause knee pain?

Sometimes. Severe pronation can drive the tibia into internal rotation, which contributes to patellofemoral pain and IT band issues in some people. The literature is mixed — not all flat-footed people develop knee pain, and not all knee pain in flat-footed patients is caused by their feet. A good biomechanical evaluation can tell you whether your specific foot mechanics are contributing.

Does the military disqualify flat feet?

Not anymore — at least not asymptomatic flat feet. The U.S. military updated its standards years ago to allow asymptomatic flatfoot. Symptomatic or severe rigid flatfoot may still be disqualifying. Check current MEPS standards if this matters for your situation.

How long is recovery from flatfoot reconstruction surgery?

Typical timeline: 6 weeks non-weight-bearing, 6 more weeks in a boot with progressive weight-bearing, then transition to athletic shoes with custom orthotics around week 12. Most patients return to low-impact activity (walking, biking, swimming) by 4-6 months and full activity by 9-12 months. Recovery varies based on which combination of procedures is performed.

The bottom line

Painless flat feet that have always been flat usually need nothing. Flat feet that hurt usually respond to properly-designed custom orthotics. Flat feet that are becoming flat in adulthood are PTTD and need urgent staging — because the window for non-surgical correction closes once the deformity becomes rigid. The single most useful thing you can do this week if you suspect a problem is the single-leg heel rise test. If you can’t do it on one side, you need a podiatrist appointment.

— Dr. Tom Biernacki, DPM, FACFAS