Can you develop flat feet as an adult?

Yes, adult-acquired flatfoot, often called posterior tibial tendon dysfunction, can occur. Ligaments and tendons supporting the arch can stretch or weaken over time due to age, weight gain, or repetitive impact from activities like running. This results in the gradual collapse of the arch, which wasn't present before.

What's the difference between flat feet and overpronation?

Flat feet (pes planus) is a structural description of a foot with a low or collapsed arch. Overpronation is a biomechanical motion — a dynamic, inward roll of the foot beyond the normal range during your gait cycle. While many people with flat feet overpronate, you can have a normal arch and still overpronate. For runners, the motion is more important than the static structure.

Is it bad to run with flat feet?

Not necessarily. Many elite athletes run successfully with flat feet. The key is managing the biomechanical stress. If your flat feet lead to excessive overpronation, it can increase the risk of injuries like shin splints or knee pain. The right supportive footwear is crucial for prevention and comfort on your runs.

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How To Tell If You Have Flat Feet: A Runner's Guide

By FlatFeetRunning Editorial · 7/26/2026 · 5 min read

To tell if you have flat feet, the simplest method is the 'wet test' to see your footprint shape. However, for runners, a more accurate assessment involves a dynamic gait analysis, ideally filmed on a treadmill. We look for a collapsing arch, significant inward ankle roll (evers…

Key takeaways

The 'wet test' is a simple starting point but can be misleading; a dynamic gait analysis is far more accurate for runners.
Professionals assess running gait by looking for signs like excessive ankle eversion and 'navicular drop' (arch collapse) on a treadmill.
The wear patterns on your old shoes are a history book; heavy wear on the inner midsole and heel strongly indicates overpronation, often linked to flat feet.
A self-diagnosis from one test isn't enough; combine multiple methods and see a professional if you have persistent pain.
Having flat feet doesn't automatically mean you'll get injured, but understanding your foot type is the first step to choosing the correct supportive shoes.

To tell if you have flat feet, the simplest check is the 'wet test' to see your footprint shape. But for runners, the most reliable assessment is a dynamic gait analysis, ideally filmed on a treadmill. In our fit sessions, we watch for a collapsing arch under load, significant inward ankle roll (eversion), and revealing wear patterns on old running shoes. This dynamic view shows how your foot functions under impact, which is what actually matters for injury prevention and choosing the right shoes.

Why the 'Wet Test' Is Just a Starting Point

The classic wet test is simple: get your feet wet, step on a dry, flat surface like concrete or a paper bag, and look at the imprint. A 'normal' arch leaves a print of the heel, the ball of the foot, and a thin strip on the outside. A flat foot leaves a print of the entire sole.

It's a decent first step, but I've seen it be wrong many times. In our studio, I once had a runner whose wet test showed a beautiful, high arch. But the moment he started running on the treadmill, his arch completely flattened and his ankle rolled inward dramatically. He had a flexible flatfoot. His arch existed when unweighted, but collapsed under the dynamic load of running. This is why we can't rely on the wet test alone; we need to see the foot in motion.

How Do Professionals Assess Flat Feet in a Running Store?

When you come in for a fitting, we use a multi-step process. We're not just looking at your arch height; we're looking at the whole chain of movement from your foot up to your knee.

The Static Test: First, we'll have you stand naturally. We look for a few things. Does the arch look low to the ground? We also perform the "too many toes" test. Looking from behind, if we can see most of your smaller toes poking out to the side of your ankle, it often indicates your foot is abducted, or splayed outward, which is common with fallen arches.
The Gait Analysis: This is the most important part. We'll have you run for a minute or two on the treadmill while we film your feet from behind. We're looking for:
- Excessive Eversion: We watch the a a joint just below the ankle, called the subtalar joint. A little inward roll (pronation) is natural and helps absorb shock. Overpronation is when that roll is excessive and the ankle joint stays angled inward for too long. We see this as a sharp inward bowing of the Achilles tendon.
- Navicular Drop: This is the technical term for your arch collapsing. The navicular is a bone at the top of your arch. We watch this spot to see how much it drops downwards when you land. A significant drop tells us the arch structure isn't supporting your weight effectively.
Shoe Wear Pattern Analysis: Your old running shoes are a diary of your biomechanics. I always ask runners to bring their old pair. For a classic overpronator with flat feet, I expect to see heavy wear on the inside edge of the outsole, especially around the heel and under the ball of the foot. I also check the midsole foam; if the inner (medial) side is crushed and compressed far more than the outer side, it’s a dead giveaway.

Static vs. Dynamic Flat Feet: What's the Difference?

Understanding whether your foot is flat all the time or only when you run is key to getting the right support. This is where many runners get confused.

Type of Flat Foot	Characteristics	What it Means for Runners
Rigid (Static) Flatfoot	Arch is flat when sitting, standing, and running. The foot structure is always flat.	Your foot has very little natural arch to collapse. You may need a shoe with a wide, straight base for inherent stability.
Flexible (Dynamic) Flatfoot	Arch is visible when sitting or on tiptoes, but flattens out when standing or running.	This is the most common type we see. Your arch collapses under load, which is where stability features like a medial post or GuideRails become critical.

Should I Film My Own Running Gait at Home?

Yes, you can absolutely get useful information by filming yourself. It won't replace a professional fitting, but it's a great tool.

Setup: Place your phone on the floor, about 5-6 feet behind a treadmill. Prop it up so it's stable and level. Aim it at your heels.
Record: Run for 60-90 seconds at your normal, easy pace. Make sure the lighting is good.
Analyze: Play the video back in slow motion. Watch one foot at a time as it lands. Does your ankle seem to roll inward significantly? Does the angle of your lower leg and heel (your calcaneal angle) look like it's collapsing inward? Compare it to videos of 'neutral' running form online. It can be an eye-opening exercise.

What I Do NOT Recommend

There are two common mistakes I see runners make. First, doing a wet test, seeing a flat footprint, and immediately buying the most rigid, heavy 'motion control' shoe on the market. These shoes can be overly corrective and stiff, and for a runner who only needs軽度 support, they can feel like a brick and sometimes even cause arch pain or shin splints. Don't over-correct.

Second, and more importantly, do not ignore sharp, persistent pain. If you have pain in your arch, heel (a common sign of plantar fasciitis), or up into your shins or knees that doesn't go away with rest, you need to see a podiatrist or physical therapist. Self-diagnosis has its limits. Our advice is for shoe selection and comfort, not for treating medical injuries.

Heads up: Our site uses affiliate links. If you buy through a link on our page, we may earn a small commission at no extra cost to you. It helps us keep the treadmills on and the cameras rolling. Thanks for your support!

So, You Have Flat Feet. What's Next?

Discovering you have flat feet isn't a sentence for injury-plagued running. It's an opportunity to get smarter about your gear. Knowledge is power. By understanding that your arch collapses dynamically, you can now look for shoes designed to counteract that specific motion.

Your next step is to explore footwear that provides stability. Modern stability shoes are fantastic—they're lighter and more comfortable than ever. They use features like firmer foam under the arch (a medial post) or holistic support systems to guide your foot into a more neutral path.

To see our top-rated shoes, start with our guide to the best running shoes for flat feet.
If you also have a wider foot, check our specific picks for wide flat feet.
Sometimes, an over-the-counter insole can provide the perfect amount of extra support. Learn more on our page about the best insoles for flat feet.
For more tips and shoe reviews, visit our main blog page.

Frequently asked questions

Can you develop flat feet as an adult?: Yes, adult-acquired flatfoot, often called posterior tibial tendon dysfunction, can occur. Ligaments and tendons supporting the arch can stretch or weaken over time due to age, weight gain, or repetitive impact from activities like running. This results in the gradual collapse of the arch, which wasn't present before.
What's the difference between flat feet and overpronation?: Flat feet (pes planus) is a structural description of a foot with a low or collapsed arch. Overpronation is a biomechanical motion — a dynamic, inward roll of the foot beyond the normal range during your gait cycle. While many people with flat feet overpronate, you can have a normal arch and still overpronate. For runners, the motion is more important than the static structure.
Is it bad to run with flat feet?: Not necessarily. Many elite athletes run successfully with flat feet. The key is managing the biomechanical stress. If your flat feet lead to excessive overpronation, it can increase the risk of injuries like shin splints or knee pain. The right supportive footwear is crucial for prevention and comfort on your runs.

FlatFeetRunning earns commissions from qualifying purchases made through links on this page. Persistent foot pain should be assessed by a podiatrist or sports physician.