Flat Feet vs Fallen Arches: What's the Difference and Does It Matter for Footwear?

If you've ever been told you have "flat feet" — or suspected you might — you've probably also come across the term "fallen arches." And if you've tried to Google the difference, you've likely ended up more confused than when you started.

As a podiatrist, I get asked about this constantly. So let's clear it up once and for all, and more importantly, talk about what it actually means for the footwear you should be wearing.

The short answer: they're related, but not the same thing — and the difference matters when you're choosing supportive sandals.

What are flat feet?

Flat feet (technically called pes planus) means the arch of your foot sits lower than average, or in some cases, touches the ground entirely when you stand. You can do a quick self-check: wet your foot and step onto a piece of paper. If you see a near-complete footprint with very little curve along the inner edge, your arches are on the flatter side.

Here's something most people don't realise though: flat feet aren't always a problem. Some people have naturally low arches their entire lives and experience zero pain or issues. Others find they cause real discomfort — aching feet, sore knees, lower back pain, or tiredness after relatively short periods of walking. The arch height itself isn't the only factor; it's whether your foot is functioning well that matters most.

What are fallen arches?

Fallen arches are different — this is when an arch that was previously normal (or higher) drops over time. It's essentially an arch that has collapsed, rather than one that was always flat.

This can happen for all sorts of reasons:

• Age — the tendons and ligaments that support the arch weaken over time
• Weight changes — increased load on the feet over a prolonged period
• Pregnancy — hormonal changes loosen ligaments, which can affect arch height (and sometimes permanently)
• Injury — particularly to the posterior tibial tendon, which is the main tendon supporting the arch
• Medical conditions — such as rheumatoid arthritis or diabetes

Fallen arches tend to cause more symptoms than lifelong flat feet, because the foot structure is changing. You might notice your shoes wearing unevenly on the inner sole, your ankles rolling inward, or a gradual onset of heel or arch pain.

So why does the difference matter for footwear?

Because the support your foot needs can be quite different depending on which one you have.

If you've always had flat feet and you're largely pain-free, you may not need a dramatic amount of corrective support — you need a footbed that accommodates your foot shape, keeps you stable, and prevents the foot from overpronating further. A deep heel cup and firm midsole matter most here.

If you have fallen arches, you're likely dealing with a foot that's become less stable over time. You may need more active arch support — something that genuinely lifts and holds the arch in a better position, rather than just contouring around it. You may also benefit from seeing a podiatrist to assess whether custom orthotics are needed alongside your footwear choices.

In both cases, what you absolutely want to avoid is:

• Completely flat sandals or flip flops — no structure means the foot is unsupported with every step
• Overly soft footbeds that feel comfortable initially but collapse quickly under body weight
• Narrow straps or poor fit — a sandal that shifts around on your foot can't do its job, however good the footbed is

The wet foot test is a start — but it's not the whole story

You might have seen advice online suggesting the wet foot test tells you everything you need to know about your arch type. It's a useful starting point, but it only tells you about your static arch height — it says nothing about how your foot behaves when you're actually walking.

Some people have a reasonable arch when standing still but overpronate significantly during their walking cycle. Others have quite flat feet structurally but have strong enough muscles and tendons to compensate well. This is why a gait analysis from a podiatrist gives you a much more complete picture.

What to look for in sandals if you have flat feet or fallen arches

Whether your flat feet are structural or acquired, the footwear principles are similar:

1. A contoured, biomechanical footbed — not just a cushioned flat surface, but one shaped to support the arch in its natural position
2. A deep heel cup — this stabilises the heel bone and reduces inward rolling at the ankle
3. A firm midsole — enough rigidity that the sandal doesn't collapse under your weight mid-step
4. Adjustable straps — so the sandal stays properly positioned on your foot throughout the day
5. A sole that resists twisting — try the twist test before you buy: if the sandal twists easily along its length, it's not going to support you

A note on Moffootwear

I designed MOFF specifically with these principles in mind — because as a podiatrist, I kept seeing the same gap. Sandals that were stylish but structurally useless, or supportive sandals that nobody actually wanted to wear.

The MOFF footbed is built around a true biomechanical last, with a contoured arch support, deep heel cup, and metatarsal support — in a leather sandal that looks like something you'd actually choose to wear. Whether you have lifelong flat feet or arches that have gradually dropped over the years, the support principles built into MOFF are designed with you in mind.

[Browse the MOFF collection here.]

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This article is for general information only and doesn't replace individual podiatric assessment. If you're experiencing foot, knee, or back pain that you think may be related to your arch type, please book an appointment with a podiatrist.