Flat Feet: When Do They Actually Need Treating?

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Expert Patient Guide  ·  Foot & Ankle Surgeon  ·  London & North London

Flat Feet When Do They Actually Need Treating?

A clear, evidence-based guide to flat feet and progressive collapsing foot deformity (formerly known as adult acquired flatfoot or posterior tibial tendon dysfunction) — written by Mr Matthew Welck, Consultant Orthopaedic Foot & Ankle Surgeon at the Royal National Orthopaedic Hospital (RNOH) and Honorary Associate Clinical Professor at UCL. Mr Welck treats NHS and private patients across London and North London, with a particular interest in foot and ankle deformity and the use of weight-bearing CT to assess how the back of the foot lines up under load.

Contents

  1. What Is a Flat Foot, Really?
  2. The Distinction That Matters Most
  3. Why the Name Changed
  4. What Causes an Arch to Collapse
  5. Symptoms, and a Self-Test That Helps
  6. Why Imaging Matters More Here
  7. Treatment: What Works Before Surgery
  8. When Surgery Is Considered
  9. Frequently Asked Questions
  10. Speak to a Specialist

01

What Is a Flat Foot, Really?

Most flat feet need no treatment at all. A low arch that has always been there, and does not hurt, is a foot shape rather than a disease. A study of 784 older adults found that common foot shape differences, flat feet included, had little relationship with pain or walking function.

The one that matters is the arch that is changing. A foot that used to have an arch and is flattening — usually on one side, usually in middle age — is a different problem entirely, and it tends to get worse if left alone.

The name for that second condition has changed. What used to be called adult acquired flatfoot or posterior tibial tendon dysfunction is now termed progressive collapsing foot deformity (PCFD), agreed by international consensus in 2020. Caught early, non-surgical treatment works well — in one structured programme of braces or insoles plus high-repetition exercises, 83% of patients with early-stage disease had a successful outcome and only 11% went on to need surgery. Left alone, a foot that is still flexible can become a stiff one, and the operations for a stiff foot are considerably bigger than those for a flexible one. That is the main reason not to wait if your arch is changing.

02

The Distinction That Matters Most

Almost every question about flat feet becomes easier to answer once you separate two quite different situations.

  • Flat feet you have always had. A low arch since childhood, usually both sides, no pain, no change over time. This is simply a normal variation in foot shape. Depending on how it is measured, somewhere between 3% and 20% of adults have it. It does not need insoles, exercises or a surgeon, and it has repeatedly been shown not to predict pain or disability.
  • An arch that is collapsing. Usually one foot. Usually starting in the forties, fifties or sixties. Often with aching along the inside of the ankle, then a visible change in shape, then difficulty rising onto tiptoes. This is a progressive condition, and it does not stay still.

If your feet have looked the same for thirty years, you are almost certainly in the first group. If shoes have started wearing unevenly, or someone has commented that one ankle looks like it is rolling in, you may be in the second — and that is worth having assessed.

03

Why the Name Changed

In 2020, an international consensus group formally recommended replacing “adult acquired flatfoot deformity” and “posterior tibial tendon dysfunction” with progressive collapsing foot deformity (PCFD). The vote to adopt it was unanimous.

The reason matters clinically. The older names put the tendon at the centre of the story, but the tendon is only part of it — the ligaments supporting the arch fail too, the heel drifts outwards, the middle of the foot turns outwards, and the main ankle bone (the talus) rotates and slips on the bone below it. Calling it a tendon problem understated what is really a three-dimensional collapse of the whole foot.

So if you have been given one label by one clinician and a different label by another, they are very likely describing the same condition. The name changed; the underlying diagnosis did not.

04

What Causes an Arch to Collapse

Most often this develops gradually, with no single injury to point to. Recognised contributing factors include:

  • Wear and tear of the tibialis posterior tendon — the tendon running behind the inner ankle bone that helps hold the arch up
  • Failure of the supporting ligaments, particularly the spring ligament and the deltoid ligament on the inner side of the ankle
  • A pre-existing low arch or tight calf, which loads these structures harder
  • Raised body weight, high blood pressure and diabetes, all linked with the condition
  • Steroid injection into the tendon, which is why injecting this particular tendon is generally avoided
  • Inflammatory arthritis, such as rheumatoid arthritis, in a smaller number of people
  • Occasionally an injury, or a tarsal coalition — two foot bones joined since birth — that only causes problems later in life

05

Symptoms, and a Self-Test That Helps

Symptoms of a collapsing arch tend to appear in a fairly consistent order:

  1. Aching along the inside of the ankle and arch, worse after standing or walking, sometimes with swelling behind the inner ankle bone
  2. Difficulty rising onto tiptoes on the affected side, or an inability to lift the heel off the ground when standing on that leg alone
  3. A visible change in shape — the arch drops, the heel tilts outwards, and more toes become visible when viewed from behind (“too many toes”)
  4. Pain moving to the outside of the ankle, a significant development, since it means the heel has drifted far enough for the bones to press against each other
  5. Stiffness — the point at which a foot that could still be moved into a better position becomes fixed

That sequence is the reason this condition rewards early assessment: stages one and two respond well to a brace and exercises, while a stiff foot generally needs joints to be fused.

A useful self-check: stand and try to rise onto tiptoes on one leg, then compare both heels from behind. In a normal foot, the heel swings inwards as you rise. If the tendon has failed, the heel stays turned out, or you cannot lift at all. It is not a diagnosis on its own, but a clear difference between the two sides is worth having assessed.

06

Why Imaging Matters More Here

Standing X-rays remain the starting point, but this is a three-dimensional deformity, and flat, two-dimensional images are affected by positioning, machine angle and bones overlapping each other.

Weight-bearing CT scans the foot in three dimensions while the patient stands on it, showing things plain films cannot reliably demonstrate: the true degree of arch collapse, how the back of the foot lines up under load, peritalar subluxation — how far the foot has rotated out from underneath the ankle bone — tilting within the ankle bone itself, and whether the heel bone is pressing against the outer ankle bone. MRI remains useful for assessing the tendon and spring ligament directly.

These measurements are not academic. They determine whether the foot is still flexible or has become fixed, which operations would be suitable, and how much correction is required — the difference between a joint-preserving reconstruction and a fusion.

07

Treatment: What Works Before Surgery

For a painless, long-standing flat foot, nothing is needed. For a painful or collapsing foot, structured non-surgical treatment should be tried properly first, and the evidence for it is better than many patients expect.

In one study of 47 consecutive patients with early-stage disease, a defined protocol — a hinged ankle-foot brace or insole, high-repetition strengthening exercises, and calf stretching — was followed for a median of ten physiotherapy visits over about four months. 83% had a successful functional outcome, 89% were satisfied, and only 11% required surgery. A separate group with a flexible stage II foot, treated with custom-moulded braces and followed for an average of five years, saw their function scores improve substantially, with the back of the foot staying flexible in all but three of eighteen patients.

The components that tend to matter most:

  • A custom insole or brace — an arch support with heel control for milder cases, a hinged ankle-foot brace where the collapse is more marked
  • Strengthening the tibialis posterior tendon, using many repetitions rather than heavy resistance
  • Calf stretching, since a tight calf makes the collapse worse
  • Weight management where relevant
  • Supportive shoes with a firm heel section

This is not simply a holding pattern before inevitable surgery. For most people with early disease, it is the treatment.

08

When Surgery Is Considered

Surgery is for pain and deformity that has not responded to a genuine trial of bracing and physiotherapy, and the choice of operation depends on whether the foot is still flexible. For a fuller explanation of the underlying condition and its non-surgical management, see our guide to adult acquired flatfoot and tibialis posterior reconstruction.

Flexible deformity — joint-preserving reconstruction. Typically a combination of cutting and shifting the heel bone to move it back under the leg, transferring a nearby tendon to take over from the failed tibialis posterior, sometimes lengthening the outer side of the foot, a calf (gastrocnemius) release, and occasionally repairing the spring ligament or fusing a single joint on the inner side of the foot. The joints themselves are preserved and movement is kept.

Fixed deformity — fusion. Where the back-of-foot joints have stiffened or become arthritic, correction means fusing them, most often a triple fusion of three joints. This reliably corrects shape and relieves pain, but the side-to-side movement at the back of the foot is lost. Where the ankle itself has tilted, treatment becomes considerably more involved, since long-standing tilt can lead to secondary ankle arthritis, which is managed separately.

The same patient, seen three years apart, may be offered a heel-bone reshaping with tendon transfer, or a triple fusion, depending on when they were seen — which is the practical case for early assessment.

Reconstruction is a bigger undertaking than most foot operations, and recovery is correspondingly longer:

StageTypical timing
Keeping weight off the foot, or walking only in a protective supportAround 6 weeks
In a boot3–6 weeks
Into a supportive shoeBy around 3 months
DrivingAround 3 months for a right foot
Desk work4–8 weeks, with elevation
Manual or standing work4–6 months
Full benefit12 months or more

Swelling after surgery to the back of the foot often lasts a year, and an insole is commonly worn afterwards. If pain has not settled some months after surgery, see our guide on what to do if you’re still in pain after foot or ankle surgery.

09

Frequently Asked Questions

Do flat feet always need treatment?

No. A painless, long-standing flat foot needs nothing. Common changes in foot shape, including flat feet, have repeatedly been shown to have little relationship with pain or walking function when they are not causing symptoms. Treatment is for symptoms and for a foot that is getting worse, not for appearance.

What is the difference between flat feet and progressive collapsing foot deformity?

Flat feet describes a foot shape, often lifelong and the same on both sides. Progressive collapsing foot deformity is a condition that develops later in life and gets worse over time, in which an arch that was previously there collapses, usually on one side and usually in middle age.

Why do I hear different names for this — PTTD, adult acquired flatfoot, PCFD?

They describe the same condition. In 2020, an international consensus recommended “progressive collapsing foot deformity” because the older names focused on the tendon and understated the three-dimensional collapse involving ligaments, the heel and the midfoot.

Do insoles fix flat feet?

They do not restore the arch permanently, but they can control symptoms effectively and are a mainstay of treatment in the early stages. In one structured protocol combining orthoses with exercises, 83% of early-stage patients avoided surgery.

Can exercises help?

Yes, in early disease. Strengthening the tibialis posterior tendon with many repetitions, together with calf stretching, is the core of the non-surgical programmes with the best published results.

Will it get worse if I do nothing?

Progressive collapsing foot deformity does tend to progress, and the important change is from a foot that is still flexible to one that has become stiff, because that changes the surgical options from reconstruction to fusion. A lifelong, painless flat foot is a different matter and does not follow this course.

Can I run with flat feet?

Many people with lifelong flat feet run without difficulty and need no intervention. Where an arch is actively collapsing, high-impact activity usually needs modifying while the condition is assessed and treated.

Should my child’s flat feet be treated?

Flexible flat feet in children are common and usually resolve or remain painless. Assessment is warranted if the foot is painful, stiff rather than flexible, or affects one side only.

Is surgery for flat feet worth it?

For carefully selected patients whose pain has not settled with bracing and physiotherapy, reconstruction reliably improves pain and function. The recovery is long, and the decision should account for that.

10

Speak to a Specialist

If your arch has changed, if one ankle is aching along the inside, or if you cannot rise onto tiptoes on one side, an assessment is worthwhile — not because surgery is likely, but because this is a condition where the treatment options narrow over time.

Mr Matthew Welck is a Consultant Orthopaedic Foot & Ankle Surgeon at the Royal National Orthopaedic Hospital, Stanmore, and Honorary Associate Clinical Professor at UCL. Foot and ankle deformity is one of his specialist interests, and he uses weight-bearing CT to assess the alignment of the back of the foot in three dimensions. He works alongside orthotists and physiotherapists across London, and sees patients in North and Central London.

Urgent same-day appointments are offered where possible.

This page is for general information and patient education only. It is not a substitute for individual medical assessment, diagnosis or treatment by a qualified healthcare professional.

References

  1. Myerson MS, Thordarson DB, Johnson JE, et al. Classification and Nomenclature: Progressive Collapsing Foot Deformity. Foot Ankle Int. 2020;41(10):1271–1276. doi:10.1177/1071100720950722
  2. Alvarez RG, Marini A, Schmitt C, Saltzman CL. Stage I and II posterior tibial tendon dysfunction treated by a structured nonoperative management protocol: an orthosis and exercise program. Foot Ankle Int. 2006;27(1):2–8. doi:10.1177/107110070602700102
  3. Krause F, Bosshard A, Lehmann O, Weber M. Shell brace for stage II posterior tibial tendon insufficiency. Foot Ankle Int. 2008;29(11):1095–1100. doi:10.3113/FAI.2008.1095
  4. Lôbo CFT, Pires EA, Bordalo-Rodrigues M, de Cesar Netto C, Godoy-Santos AL. Imaging of progressive collapsing foot deformity with emphasis on the role of weightbearing cone beam CT. Skeletal Radiol. 2022;51(6):1127–1141. doi:10.1007/s00256-021-03942-1
  5. Badlissi F, Dunn JE, Link CL, Keysor JJ, McKinlay JB, Felson DT. Foot musculoskeletal disorders, pain, and foot-related functional limitation in older persons. J Am Geriatr Soc. 2005;53(6):1029–1033. doi:10.1111/j.1532-5415.2005.53315.x

Study data above retrieved via PubMed.

Written by: Matthew Welck | Consultant Orthopaedic Foot & Ankle Surgeon London — last updated 20 August 2026

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