Flat feet, also called pes planus, is a deformity that occurs when the arch of the foot collapses and comes into complete or near-complete contact with the ground. The condition may be congenital (occurring at the time of birth) or acquired (developing over time, most often as a result of age or injury).
Diagnosis of flat feet typically involves a visual examination of the foot, supported by imaging tests. Treatments may involve over-the-counter pain medications, orthotic arch supports, foot exercises and, less commonly, surgery.
Between 20 percent and 30 percent of the general population has some degree of flat-footedness.1
While most people with flat feet have few, if any, symptoms, those who do typically experience pain in the midfoot region. The pain tends to increase with activity and may be accompanied by swelling along the inner ankle and arch.
Hip, knee, and lower back pain are also common as the instability of your gait and posture can place undue stress on these joints 2 Over time, simple movements like standing on your toes can become unbearable as arthritis further limits the range of motion between the bones of your foot. This can affect how you walk or run, leading to a characteristic flat-footed gait.
Flat feet are typically associated with excessive pronation of the foot.3 As opposed to normal pronation (in which the foot rolls evenly from the heel to toe), overpronation occurs when the arch descends downward and inward as the foot strikes the ground.
Because of their tendency to overpronate, flat feet are less able to absorb shock, placing persistent stress on the feet, ankles, and knees. Overpronation causes the excessive rotation of the tibia (shin bone), increasing the risk of shin splints.
The inward tilt of the foot places further strain on the tendons and ligaments of the lower extremities. Achilles tendinitis (inflammation of the Achilles tendon) and knee pain are common consequences.
The cause and treatment of flat feet differ based on the person's age. Flat feet in children will often resolve without intervention, while "fallen arches" in adults tend to be permanent and non-reversible.
Flat Feet in Children
Flat feet in newborns and toddlers is normal because the arches of haven’t yet developed. While most children will develop arches by the age of 3,5 some may experience delays or have structural deformities that interfere with the normal alignment of the foot bones.
Flat feet are commonly associated with genetic disorders that first develop in childhood, including:
Calcaneovalgus (excessive bowing of the calf bone)
Congenital vertical talus (congenital flat foot)6
Dyspraxia (developmental coordination disorder)
Ehlers-Danlos syndrome (a congenital disease that increases the elasticity of skin, joints, and blood vessels)7
Ligamentous laxity (loose ligaments)
Metatarsus adductus (inward-pointing toes)
Tarsal coalitions (congenitally fused foot bones)
Flat feet may come and go as a child develops. During growth spurts, changes in the tightness of the calf muscles may cause temporary flat-footedness. A similar example is genu valgum, also known as knock-knees, which usually occurs between the ages of 2 and 5, and typically corrects itself during adolescence.8
In some children, flat-footedness will not right itself. While there may be no outward explanation for this, obesity can often contribute by placing additional stress on a still-developing foot.
Flat feet in children may only become apparent between adolescence and the early teen years when abnormalities in gait and pronation become more apparent. If left untreated, the disorder can progress and worsen in later life.
Flat Feet in Adults
"Fallen arches" is a term used to describe the collapse of the bones and connective tissues of the midfoot. It is commonly associated with the deterioration of the posterior tibial tendon, which runs along your inner ankle. Faulty foot mechanics can also take their toll on the structure of arch, leading the progressive loosening of ligaments that support the foot bones.
A fallen arch (also known as an adult-acquired flat foot) occurs most commonly in women over 40 and people who are obese.9 Hypertension and diabetes can also contribute by affecting the blood flow to the muscles and connective tissues of the foot. A past injury, such as a stress fracture, may also lead to a fallen arch.
Among some of the other conditions linked to adult-acquired flat foot:
Leg length inequality can cause flat-footedness by forcing the longer limb to compensate by flattening the arch.
Pregnancy can cause temporary or permanent flat-footedness due to the increased production of elastin, a protein that increases the elasticity of skin and connective tissues.9
Marfan's syndrome is a genetic disorder usually diagnosed in one's 30s that also affects connective tissues.
Rheumatoid arthritis is an autoimmune form of arthritis in which the immune system attacks its own joints.
Scoliosis, the abnormal curvature of the spine, can cause an uneven and unstable gait, leading to unilateral (one-sided) flat-footedness.10
Shoes can also contribute. A compressed toe box (which prevents the toes from resting in a natural position) and an elevated heel (which causes hyperextension of the arch muscles and decreased dorsiflexion of the ankle) all serve to undermine the strength and flexibility of the underside of the foot, increasing the risk of collapse.
Fallen arches are almost always permanent. With that being said, many people will have a condition known as flexible flat foot in which the arch is visible when the foot is lifted but disappears once the foot is placed on the ground. Flexible flat feet can result in pain in the foot, along the shin bone, and in the lower back, hip, or knee.11
However, as a person ages, the condition can worsen and cause the collapse of one or both arches. Over time, this can lead to a condition known as rigid flat foot in which the sole is rigidly flat even when the foot is lifted.
While flat feet can usually be self-diagnosed, the underlying cause may require investigation by a foot specialist known as a podiatrist. This may involve a visual exam as well as imaging tests to evaluate the structure of the foot.
A podiatrist can usually diagnose flat feet by looking at your feet while standing. Among some of the visual tests used:
The wet footprint test is performed by wetting the feet and standing on a smooth, level surface. The thicker the print between the heel and ball of the foot, the flatter the foot. By contrast, a high-arch foot would leave only a narrow print of the outer foot.
The shoe inspection test can provide evidence of faulty foot mechanics. If you have flat feet, there will be more wear on the inside of your sole, especially in the heel area. The shoe's upper will also tend to lean inward over the sole.
The "too many toes" test is performed as the doctor stands behind you and counts the number of toes peeking out to the sides. While only the pinky toe would be seen in people with normal pronation, three or four may be seen in those who overpronate.
The tiptoe test is used to see if you have flexible or rigid flat feet. If a visible arch forms when you stand on your toes, you have flexible flat feet. If not, your doctor would likely recommend treatment for a rigid flat foot.
If you are experiencing a lot of foot pain, your doctor may order imaging tests to help pinpoint the underlying cause. Among the imaging tests used:
X-rays and computed tomography (CT) scans are ideal for diagnosing arthritis and evaluating irregularities in the angle and/or alignment of the foot bones.
Ultrasound can be used to produce detailed images of soft tissue damage, such as a ruptured tendon.
Magnetic resonance imaging (MRI) can provide detailed images of bone and soft tissue damage, ideal for people with rheumatoid arthritis, tendonitis, or an Achilles heel injury.
The treatment of flat feet can vary in children and adults. In either case, a conservative approach is usually preferred with surgery reserved for only the more severe cases.
Treatment in Children
By and large, flat feet in children do not require treatment and will usually develop arches by adolescence or early adulthood.
Children who go barefoot on varied terrain are more likely to have normal arch development, usually between the ages of 4 and 6.12 By contrast, closed-toe shoes (particularly those with narrow toes) may have the opposite effect, increasing the risk of lax ligaments.
The current body of evidence suggests that the use of orthotics in children with flat feet is rarely beneficial.13 The only exception may be in children with congenital foot deformities. In these cases, surgery would be performed no later than the early teens, when the bone structure is still developing. Orthotics would then be used to ensure the foot heals in the correct position.
Non-Surgical Treatment in Adults
Fallen arches in adults often require no treatment. People with persistent or severe symptoms may benefit from orthotic arch supports and foot gymnastics. Before surgery is considered, conservative treatments such as non-steroidal anti-inflammatory medications (NSAIDs), corticosteroids, and orthotics or bracing are tried.14
Orthotic supports are used to change the structure of your foot. Over the course of weeks or months, layers will be added, allowing you to gradually adapt to the sensation with minimal discomfort. Once prescribed, arch supports should be worn for the rest of your life.
Treatment should also include exercises that increase arch flexibility and strength. Among the techniques commonly used by podiatrists and physical therapists:
Foot gymnastics involves activities that strengthen the intrinsic muscles of the foot. This may include picking up marbles with your toes, stacking items with your toes, or writing numbers in the sand with your big toe.
A runner’s stretch may be used to lengthen your calf muscle and Achilles tendon, both of which can impair pronation when tight.
Downward dog is a yoga pose that also aims to lengthen and strengthen the calf muscle and Achilles tendon.
Therapeutic massages, such as rolling a ball under your foot, may help improve arch flexibility while alleviating aches and pains.
If needed, flat foot surgery can provide lasting pain relief and may even create an arch where none existed. Because the causes and location of the pain can vary, no two surgeries are ever alike. The surgical approach will ultimately be based on your age, your symptoms, and the nature of the structural deformity.
There are two main types of surgery to treat flat feet. The most common is reconstructive surgery, which repositions the tendons and fuses certain joints to properly realign the foot. Another procedure uses a subtalar implant to support the arch. The metal implant is put in the back of the foot to correct flat feet.
Foot surgery can be costly and may require extensive recovery time. Moreover, insurance companies tend to be reluctant to approve the procedure until all other options have been exhausted. Even then, approvals can be a challenge.
In some cases, approvals will only be obtained after an acute injury, such as a tendon rupture, leaves the doctor with no other option but surgery.
If you suffer symptoms of flat feet, the first course of action is to find shoes that compensate for the abnormal structure of your foot. While there are companies that can custom-make corrective shoes, it is usually a costly process.
A somewhat less costly option is to have custom-made insoles, which you can slip in and out of your pairs of shoes as needed. Some online retailers will send you a plasticine slab to create the foot mold, which they can use to create different types of insoles for running, walking, or work. The cost is usually between $100 to $150 per pair.
But in many cases, custom-made shoes or orthotics are not necessary. All you may really need is the appropriate shoe fitted properly. Surprisingly, many foot problems stem from wearing poorly fitted and sized shoes.
When selecting shoes, invest in those that compensate for any abnormalities in your gait. Examples include:
Stability shoes if you have a neutral stride or mild overpronation
Motion-control shoes if you have significant overpronation
Comfort shoes that support your arches and do not bend in the middle of the sole
Shoes with removable insoles (taking them out should give you enough space to insert over-the-counter or prescription orthotics)
The shoes should bend at the toe to allow natural foot movement rather than having a completely rigid sole. You should also avoid shoes with high arches as this may cause pain and bruising.
A Word From Verywell
Many people will wait to see a podiatrist until their foot pain becomes unbearable. The problem with this is that any damage done to the foot may already be irreversible or difficult to correct.
In the end, you need to see a podiatrist if the discomfort is keeping you from walking, standing, or exercising. The same applies if you find yourself favoring one foot over the other. By treating these conditions early, you may be able to prevent knee, hip, or lower back pain in later life.
A podiatrist will be able to recommend insoles or orthotics appropriate to your foot and direct you to the best store to get properly fitted shoes. Prescription foot orthotics are sometimes covered by health insurance under the durable goods benefit.