A
Anurag
Anurag
Published Date22 Sept'26
Last Updated22 Sept'26
Read Time17 Minutes
About
Flat feet and fallen arches are terms that are often used interchangeably, but they can describe different ways an arch can be low or absent.
In simple terms, flat feet describe the position or structure of the foot when the arch is reduced or absent, while “fallen arches” commonly refers to an arch that has become lower over time, particularly after it previously developed normally. However, terminology varies between healthcare sources, and some organizations use “fallen arches” simply as another term for flat feet.
This distinction matters because someone who has always had flexible flat feet may have a very different situation from an adult whose previously developed arch has progressively flattened, particularly when pain, swelling or changes in foot shape are present.
In this guide, we'll explain:
The difference between flat feet and fallen arches Whether flat feet and fallen arches are actually the same What causes each condition How childhood flat feet differ from adult-acquired flatfoot Signs that an arch may have fallen over time The role of the posterior tibial tendon Whether fallen arches can be reversed When flat feet or fallen arches may require professional assessment How arch support fits into the picture
Not always.
The terms overlap, but the context in which the flat foot occurs is important.
Flat feet generally describe a foot in which the medial arch is low or absent, particularly while standing. Flat feet can be flexible or rigid and may be present from childhood or develop later in life.
Fallen arches commonly refers to a foot that has become flatter after the arch previously developed. This is often discussed in relation to adult-acquired flatfoot or progressive collapsing foot deformity.
However, terminology isn't completely consistent.
For example, the NHS uses “flat feet” and “fallen arches” as alternative terms, while Cleveland Clinic and the American College of Foot and Ankle Surgeons distinguish acquired flatfoot/fallen arches from flat feet that may have been present since childhood.
So the most useful distinction is not simply the name used, but whether the arch:
Was naturally low from childhood, or
Previously developed and subsequently became lower.
| Feature | Flat Feet | Fallen Arches |
|---|---|---|
| What does it describe? | Low or absent arch | An arch that has become lower |
| Can it be present from childhood? | Yes | Usually refers to later development |
| Can it develop in adulthood? | Yes | Yes |
| Is it always painful? | No | No |
| Can it be flexible? | Yes | Yes, especially earlier |
| Can it be rigid? | Yes | Advanced acquired flatfoot can become stiff |
| Can one foot be affected? | Possible | Common in acquired cases |
| Does it always worsen? | No | Some acquired conditions can progress |
| Is treatment always needed? | No | Not necessarily, but new/progressive symptoms warrant assessment |
A major point to remember is that having a low arch does not automatically mean that the arch has “fallen.”
Some people simply have naturally low arches throughout life and remain active and pain-free. NHS patient information notes that many adults have flat-foot posture that has continued from childhood and that this is often asymptomatic.
Flat feet, also called pes planus, are feet in which the inner arch is reduced or appears to contact the ground during weight-bearing.
Flat feet can occur in children and adults.
They can also be:
Flexible
Rigid
Present from childhood
Acquired later in life
Symptomatic
Completely painless
Cleveland Clinic describes flexible flat feet as the most common type. With flexible flat feet, an arch can usually be seen when the foot isn't bearing weight but disappears when standing.
This is particularly common in children.
The arch may become visible when a child:
Sits down
Has the foot relaxed
Stands on tiptoes
An NHS pediatric resource describes this as a typical characteristic of a flexible flat foot.
No.
Flat feet are common and often cause no symptoms.
The NHS states that flat feet usually do not cause problems and generally should not prevent normal activities, including sports.
Therefore, the visual appearance of a low arch alone doesn't tell you whether a foot is healthy or problematic.
“Fallen arches” is commonly used to describe an arch that has become lower or collapsed, particularly after the foot has developed a normal arch.
Foot Health Facts describes fallen arches as a term commonly used for a flatfoot condition that develops during adulthood.
Cleveland Clinic uses the term acquired flat foot for flat feet that occur after the feet have developed their natural arches and also refers to this as fallen arches or progressive collapsing foot deformity.
This is different from someone who has had a low arch since childhood.
Example
Imagine two people:
Person A
Their arches have always been relatively low. They have no pain, can walk and run normally, and their foot shape has remained stable.
Person B
They had visible arches as an adult. Several years later, one arch becomes noticeably lower, the foot changes shape and they develop pain around the inside of the ankle.
Although both people may now appear to have “flat feet,” the underlying situation may be quite different.
Person B may have acquired flatfoot/fallen arch and should be assessed, particularly if the change is progressive or painful.
Flat feet can have many causes, and sometimes there is no specific disease or injury responsible.
Normal developmental variation
Young children commonly have flat-looking feet while their arches are developing.
The arch often becomes more apparent during childhood, although some people continue to have low arches as adults.
Genetics
Some people naturally have flatter arches because of inherited foot structure.
Flexible joints and ligaments
A flexible foot may flatten when it bears weight but regain an arch when unloaded or when standing on tiptoes.
Structural differences
Some people have anatomical differences that prevent a normal arch from developing or maintaining its shape.
Acquired conditions
Flat feet can also develop later due to tendon problems, injury, arthritis and other conditions affecting the structures that support the arch.
For a deeper explanation of low arches specifically, see:
What Is a Low Foot Arch? Causes, Signs & Support Options
Fallen arches that develop after an arch was previously present can have several possible causes.
One of the most important structures involved is the posterior tibial tendon.
The posterior tibial tendon runs behind the inside of the ankle and helps support the arch.
If the tendon becomes weakened, stretched or damaged, its ability to support the arch can decrease.
Foot Health Facts identifies posterior tibial tendon dysfunction as a major cause of adult-acquired flatfoot and explains that reduced tendon function can result in flattening of the foot.
The Royal National Orthopaedic Hospital similarly explains that the tibialis posterior tendon helps support the arch and that dysfunction can contribute to progressive flattening.
Depending on the individual, acquired arch flattening can also be associated with:
Foot or ankle injury
Ligament problems
Arthritis
Diabetes-related foot complications
Increased mechanical loading
Age-related changes
Inflammatory conditions
Pregnancy
Higher body weight
These factors don't mean that everyone with them will develop fallen arches. They are potential contributors rather than a diagnosis by themselves.
Yes.
Although some people have flat feet because their arches never became prominent during childhood, the arch can also become flatter later in life.
Cleveland Clinic classifies flat feet as either congenital or acquired and describes acquired flat foot as occurring after the natural arches have already developed.
This is why the phrase “fallen arch” is often used for adult-acquired flatfoot.
However, a new low arch in adulthood is different from someone who has had the same foot shape since childhood.
Yes, an arch can become lower over time.
The change may be gradual rather than sudden.
In adult-acquired flatfoot, problems affecting the structures that support the arch can cause progressive flattening. Posterior tibial tendon dysfunction is one important example.
This is also why a new change in arch height deserves more attention than a stable low arch that has always been present.
For a broader discussion of how foot arches can change throughout life, see:
Can Your Foot Arch Change Over Time?
There is no reliable way to diagnose a fallen arch simply by looking at your footprint.
Instead, look for a change from your previous foot structure, particularly if the change is accompanied by symptoms.
Possible signs include:
1. Your arch looks noticeably lower
You may notice that the space beneath the inside of your foot has decreased compared with the past.
2. Your foot shape has changed
The foot may appear longer or wider, or the heel may sit in a different position.
3. Pain along the inside of the ankle or foot
Pain or tenderness along the inside of the ankle can occur when the posterior tibial tendon is affected.
4. Swelling
Swelling along the inside of the ankle can accompany posterior tibial tendon problems.
5. Difficulty standing on one tiptoe
A healthcare professional may assess the ability to perform a single-leg heel raise when evaluating acquired flatfoot.
6. One foot looks different from the other
Adult-acquired flatfoot may affect one foot more than the other. Foot Health Facts notes that posterior tibial tendon dysfunction commonly occurs in one foot, although both feet can be affected.
Yes.
This is one of the most important distinctions in this article.
Someone can have flat feet because their arches have always been low.
They may have:
No pain
Normal walking
Normal running
Normal balance
Normal participation in sports
Stable foot shape
In this situation, there may be no evidence that the arch has “fallen.”
NHS guidance notes that many adults have a flat-foot posture that has continued from childhood and that this is often normal and symptom-free.
Yes.
An arch becoming lower does not automatically mean that pain will occur.
However, a newly developing or progressively worsening flat foot should not be dismissed simply because it is painless, particularly if the foot shape is changing noticeably.
The NHS notes that flat feet are usually harmless, but symptoms such as ankle, lower-leg or inner-foot pain can occur.
If you have noticed a significant recent change in your arch, particularly on one side, professional assessment can help determine what is causing it.
The difference becomes clearer when we compare the typical patterns.
Often:
Both feet are affected
The feet are flexible
The arch may appear on tiptoes
There may be no pain
Foot shape may remain stable
Normal activities are usually possible
May involve:
A previously visible arch
Progressive flattening
One foot being more affected
Inner ankle or arch pain
Swelling
Changes in foot alignment
Difficulty with certain activities
This distinction is clinically relevant because acquired flatfoot can sometimes progress. Cleveland Clinic notes that some types and causes of flat feet can worsen over time.
These terms describe different characteristics and shouldn't automatically be treated as opposites.
A flexible flat foot describes how the arch behaves.
A fallen arch describes a reduction or loss of arch height, often referring to acquired change.
For example, an acquired flat foot may initially remain flexible before becoming more rigid as the condition progresses.
When standing:
Arch ↓
When sitting or standing on tiptoes:
Arch ↑
When standing:
Arch ↓
When sitting:
Arch remains reduced
A flexible flat foot is common and often asymptomatic, particularly in children.
Not necessarily.
A low arch describes the height of the arch.
A fallen arch generally suggests that the arch has become lower than it was previously.
This is an important distinction for understanding your own foot structure.
For example:
Someone can naturally have a low arch without ever having experienced an arch collapse.
This is why you shouldn't assume that every person with a low arch has a condition requiring treatment.
For a deeper explanation of low arches, read:
What Is a Low Foot Arch? Causes, Signs & Support Options
No.
These terms describe different things.
Fallen arch / flat foot: describes the structure or posture of the foot.
Overpronation: describes excessive inward rolling of the foot during movement.
Cleveland Clinic specifically distinguishes overpronation from flat feet, noting that overpronation relates to gait while flat feet refer to reduced arch height.
They can occur together, but they are not interchangeable terms.
Yes, a person who already has relatively flat feet may experience further flattening later in life.
Having a naturally low arch may also increase the amount of load placed on some supporting structures, but it does not mean that progression is inevitable.
The Royal National Orthopaedic Hospital notes that people who already have flat feet can develop changes involving the posterior tibial tendon, with the arch subsequently flattening further.
So:
Low arch ≠ inevitable fallen arch.
It depends on the cause, severity and stage.
There is no single treatment that reverses every fallen arch.
For mild or early acquired flatfoot, management may include combinations of:
Activity modification
Appropriate footwear
Orthoses or insoles
Physiotherapy
Strengthening
Stretching
Pain management
The Royal National Orthopaedic Hospital notes that treatment for posterior tibial tendon dysfunction can include footwear changes, orthoses and physiotherapy depending on the stage and individual circumstances.
More advanced structural changes may require specialist treatment.
Therefore, it is better to ask:
“What is causing my arch to flatten, and how advanced is the problem?”
rather than assuming that every fallen arch can simply be restored to its previous shape.
Arch support can sometimes be part of managing symptoms or mechanical loading, depending on the cause.
However, an arch-support product should not automatically be viewed as a way to permanently rebuild a collapsed anatomical arch.
For people with acquired flatfoot, clinicians may use orthoses to improve foot stability and reduce strain on affected structures. The Royal National Orthopaedic Hospital describes orthoses as one component of nonsurgical management for tibialis posterior tendon dysfunction.
For a broader explanation of what arch support does, see:
What Does Arch Support Do? Benefits, Uses & Who Needs It
You can also explore: Can Arch Support Improve Foot Comfort? What the Evidence Says
The appropriate level of support depends on the person's foot structure, symptoms, activity and underlying cause.
It would be too strong to claim that wearing arch-support products prevents all cases of fallen arches.
Arch flattening can involve multiple structures and causes, including tendon problems, injury, arthritis and other conditions.
Footwear and orthoses may be useful for comfort or mechanical support in some people, but they shouldn't be presented as a guaranteed way to prevent an acquired flatfoot condition.
A low arch that has been present for years and causes no problems is generally different from a new, painful or progressively changing arch.
Consider professional evaluation if you notice:
New or increasing arch pain
Pain behind or below the inside of the ankle
Persistent swelling
One foot becoming flatter than the other
A noticeable change in foot shape
Difficulty standing on one tiptoe
Difficulty walking or running
Increasing fatigue with activity
Reduced ability to participate in normal activities
A rigid or increasingly stiff flat foot
Foot Health Facts emphasizes the importance of early evaluation for painful adult-acquired flatfoot because the condition can become more difficult to manage as deformity progresses.
The Royal National Orthopaedic Hospital similarly describes adult-acquired flatfoot as a condition that can progress through different stages.
You can make some simple observations at home, but they don't establish the underlying cause.
Look at your feet while standing
Look at the inside edge of each foot.
A reduced or absent visible arch while standing may indicate flat feet.
Compare both feet
Look for significant differences between the two sides.
Stand on your tiptoes
If it is safe and comfortable, observe whether an arch becomes visible.
A flexible flat foot commonly shows an arch when the foot is unloaded or when standing on tiptoes.
Think about history
Ask yourself:
“Have my feet always looked like this?”
versus:
“Has my arch recently become lower?”
That historical difference is particularly important when considering whether a flat foot may represent an acquired fallen arch.
For a more detailed at-home arch assessment, see:
How to Tell What Type of Foot Arch You Have
You can also read: How to Measure Your Foot Arch at Home
A wet-foot test can show how much of the sole contacts the ground, but it cannot tell you by itself whether your arch has fallen.
Why?
Because a footprint doesn't tell you:
What your arch looked like previously
Whether your foot is flexible or rigid
Whether a tendon is functioning normally
Whether there is an underlying injury
Whether the foot is painful
Why the arch is low
For that reason, use a wet footprint as an observational tool rather than a diagnosis.
See: Wet Foot Test: How to Check Your Arch Type at Home
for a detailed explanation of how the test works and its limitations.
The most important question isn't always:
“How high is my arch?”
It can be:
“Has my arch always been this way, or has it changed?”
A stable, flexible, painless low arch may simply be part of your natural foot structure.
A newly flattened arch accompanied by pain, swelling, asymmetry or functional changes may indicate an acquired problem that deserves assessment.
This distinction is particularly important because the terms flat feet, fallen arches, acquired flatfoot and pes planus are not used identically by every source.
Flat feet and fallen arches overlap, but they aren't always the same concept.
Flat feet describe a low or absent arch, particularly during weight-bearing.
A person can have flat feet from childhood without ever having experienced an arch collapse.
Fallen arches commonly refers to an arch that becomes lower after previously developing.
Adult-acquired flatfoot is one context in which the term fallen arches is commonly used.
Posterior tibial tendon dysfunction is an important cause of acquired flatfoot.
Not every flat foot is painful or requires treatment.
A new, progressive or painful change in arch height deserves more attention than a stable low arch.
Flat feet and overpronation are related concepts but describe different things.
Arch-support products may be used as part of symptom or mechanical management in some situations, but they should not be presented as a guaranteed way to permanently rebuild an arch.
If one arch has recently changed shape, particularly with pain or swelling, professional assessment can help identify the underlying cause.
FAQs
