Being flat footed means the arches on the inside of your feet are flattened, allowing the entire sole to touch or nearly touch the ground when you stand. It’s one of the most common foot variations, affecting millions of people. Most cases cause no pain at all, but for some, flat feet lead to discomfort in the ankles, arches, and even the knees or hips over time.
How the Foot Arch Works
Your foot has a natural curve along the inner edge called the medial longitudinal arch. This arch acts like a spring, absorbing shock when you walk, run, or jump. It’s held up by a network of bones, ligaments, and a key tendon that runs along the inside of your ankle and attaches to the bones in the middle of your foot. When any part of this support system weakens or stretches out, the arch drops and the foot flattens.
Flexible vs. Rigid Flat Feet
Not all flat feet behave the same way. The distinction between flexible and rigid types matters because it determines what you’ll experience and what kind of care makes sense.
Flexible flat feet are by far the more common type. If you sit down and look at your feet, you’ll see an arch. But when you stand up and put weight on them, the arch disappears. This is the kind most children and many adults have, and it often causes no symptoms at all.
Rigid flat feet show no arch whether you’re standing or sitting. People with rigid flat feet may find it difficult to move their feet up and down or side to side. This type is more likely to cause stiffness and pain and is more likely to need medical attention.
Why Most Children Have Flat Feet
Virtually all toddlers start out flat footed. Research published in Frontiers in Pediatrics found that 97% of children aged 2 or younger had flat feet based on footprint measurements. That number dropped to just 4% among 10-year-olds. The arch gradually forms as the bones, muscles, and ligaments in the foot mature through childhood. So a flat-footed toddler is almost never a cause for concern.
Causes in Adults
When flat feet develop later in life, the most common culprit is a breakdown of the posterior tibial tendon, the tendon running behind your inner ankle bone that holds the arch up. Over years of repetitive stress, this tendon can weaken and stretch, allowing the arch to collapse. Once this tendon loses tension, the outer ankle muscles pull the heel outward unopposed, which worsens the deformity.
Several factors accelerate this process. Obesity increases the mechanical load on the tendon with every step. Inflammatory conditions like rheumatoid arthritis can weaken the tendon from the inside. Diabetes, high blood pressure, and steroid use are also linked to faster tendon degeneration. An acute injury, such as a bad ankle sprain, can damage the tendon or the ligaments that support the arch and trigger a sudden flattening. Even having a naturally flat or flexible foot in childhood can make you more vulnerable to a progressive collapse later on.
In some cases, the tendon is fine but the spring ligament (a thick band connecting the heel bone to the bone just in front of it) fails on its own, producing the same result.
What Flat Feet Feel Like
Many people with flat feet never feel a thing. When symptoms do appear, they typically show up as pain along the inner ankle, in the arch, or on the outer edge of the foot. The pain tends to worsen with activity, especially walking or standing for long stretches, and eases with rest.
Because the body works as a connected chain, a collapsed arch can ripple upward. When the foot flattens, it rolls inward (overpronation), which forces the shin to rotate inward. This changes the angle at the knee and hip. Research on lower-extremity mechanics has shown that increased foot pronation leads to greater internal rotation at both the knee and hip joints. Over time, this can contribute to knee pain, hip discomfort, or lower back stiffness, especially in people who are active or on their feet all day.
How Flat Feet Are Diagnosed
A podiatrist or orthopedic specialist can usually identify flat feet just by watching you stand, walk, and examining your foot’s shape and flexibility. They’ll look at whether the arch appears when you rise onto your toes (a sign of flexible flat feet) or stays flat no matter what.
If imaging is needed, weight-bearing X-rays taken from the side give the clearest picture. Doctors measure specific angles between the foot bones. One of the most reliable is the calcaneal pitch, which looks at how steeply the heel bone tilts relative to the ground. A calcaneal pitch below about 12 degrees is a strong indicator of flat feet. Other angles, such as the alignment between the ankle bone and the first long bone of the foot, help confirm severity and guide treatment decisions.
Managing Flat Feet Without Surgery
The first line of treatment is almost always conservative, and it works well for the majority of people.
Orthotics and insoles are the most widely used option. Both prefabricated (off-the-shelf) inserts and custom-molded orthotics have been shown to improve foot function within one to three months. One randomized trial of 142 participants found that inexpensive prefabricated insoles provided similar pain relief and functional improvement compared to custom orthotics that cost significantly more. Custom orthotics may still make sense for unusual foot shapes or severe cases, but for most people, a well-made over-the-counter insert is a reasonable place to start.
Supportive footwear matters too. Shoes with structured arch support and a firm heel counter prevent the foot from rolling inward as much, reducing strain on the tendon and ligaments.
Targeted exercises can strengthen the small, deep muscles inside the foot that help maintain the arch. A few that have evidence behind them:
- Arch lifts (foot doming): While standing with your foot flat on the floor, try to raise just the arch by pulling the ball of your foot toward your heel without curling your toes. This activates the intrinsic foot muscles and has also shown benefits for conditions like plantar fasciitis.
- Marble pickups: Place a handful of marbles on the floor and use your toes to pick them up one at a time and drop them into a cup.
- Towel curls: Lay a towel flat on the floor, place your foot on one end, and use your toes to scrunch the towel toward you.
Calf stretching is also helpful. A tight calf muscle increases downward force on the arch with every step, so keeping the calves flexible reduces strain on the structures holding the arch up.
When Surgery Becomes an Option
Surgery is reserved for people with significant pain or deformity that hasn’t improved after months of conservative treatment. The specific procedure depends on how far the deformity has progressed and whether the joints are still flexible or have become rigid.
For flexible flat feet, surgeons may shift the heel bone back into better alignment, lengthen the outer column of the foot, or transfer a nearby tendon to take over the job of the failing one. These procedures aim to restore the arch and rebalance the foot while preserving joint motion. For rigid flat feet with arthritis or fixed deformity, fusing two or three joints in the back of the foot is sometimes necessary. This eliminates painful motion at those joints and locks the foot into a corrected position. Recovery from flat foot surgery typically involves several weeks of non-weight-bearing followed by a gradual return to activity over three to six months.