Pes planus, more commonly known as flat feet, involves flattening in the normal arch of the foot. Pes planus can be congenital, meaning from birth, or acquired, meaning not caused from birth and developed later in life. With flat feet, there is a decreased arch on the side of the feet, leading to the entire foot surface contacting the ground when walking.
Pes planus is also known as flat feet.
Pes planus involves a flattening of the normal foot arch in an area medically described as the medial longitudinal arch.
Pes planus can be congenital, meaning from birth, or acquired, meaning not caused from birth and developed later in life.
Treatment of pes planus usually involves treating the symptoms, including orthotics, arch supports, physical therapy, medications, and surgical treatment (in rare cases).
The anatomy of a flat foot
As seen in the image, the foot on the left has a normal arch, while the one on the right is a foot with a flat arch. If you're curious if you have a flat foot, you can look at the imprint your foot makes on the floor after getting out of a pool or shower — the flat foot will leave more of a water imprint than a normal arched foot.
If you notice on the imprints in the picture, the foot's outside area (lateral side) is the same for normal and flat feet, the difference is on the medial (middle) side. Thus, flat feet mean a lack of curvature of the medial arch, called the medial longitudinal arch since it is on the medial side and longitudinal (lengthwise).
Also, during normal walking, the foot undergoes pronation — rolls inward — for shock-absorbing reasons. Pronation involves the outside of the foot's sole contacting the surface first, then the foot rolls, and the medial side contacts the surface.
Pronation is a normal process. However, people with flat feet tend to pronate excessively, a process called overpronation.
Causes of flat feet
There are two categories of flat feet causes: congenital and acquired.
- Congenital. In these cases, people are born with flat feet, but the condition is not evident until ages 5–6 when the normal foot arch is supposed to develop but doesn't.
- Acquired. Acquired flat feet can develop from a specific injury (trauma) and cumulative trauma (repetitive or overuse injuries). In addition, acquired flat feet can be from tight muscles and tendons in the lower extremities, including the calf muscle and Achilles tendon.
Conditions that place additional stress on the muscles and tendons increase the risk of acquired flat feet, including obesity, diabetes, and inflammatory conditions like rheumatoid arthritis.
Approximately 20–37% of the population has some degree of pes planus (flat feet). However, there is a higher percentage of African Americans with pes planus compared to non-Hispanic whites. Additionally, the ratio of men to women is even. Because pes planus often runs in families, it is believed to have a genetic component.
How flat feet are diagnosed?
A history may elicit symptoms of pain in the foot, leg, knee, hip, or back. However, some adults with flat feet do not have any symptoms. Due to the overpronation with flat feet (discussed above), there can be a history of ankle rolling, causing ankle and foot pain.
In addition to pain, people with flat feet may develop lower extremity muscle cramps.
In a physical exam, the physician or medical provider should perform the following:
- Touch and press on the entire foot to check the arch and areas of tenderness.
- Check the range of motion of the foot and ankle.
- Muscle strength testing by using resistance to movement and having you stand on your toes and heels.
- Evaluate your pattern of walking by watching you walk. Sometimes the overpronation is visible.
Imaging studies like plain X-rays should be done. For example, if pes planus is suspected, the foot X-rays should be done while standing instead of lying on the X-ray table. These X-rays can also help evaluate the degree of flattening in the medial longitudinal arch.
In addition, plain X-rays can help evaluate for underlying bony diseases such as arthritis, fractures, or osteoporosis.
If an evaluation of muscles, tendons, or ligaments is needed, a magnetic resonance imaging (MRI) test can be done. However, an ultrasound test can evaluate if a tendon is torn — and is simpler and less expensive than an MRI.
Flat feet treatment options
Most people with flat feet do not require treatment. However, conservative treatment should be initiated if there is pain in the feet, legs, knees, or low back due to pes planus.
The treatment methods discussed below will not cure flat feet, but they may help with the symptoms.
- Arch supports and orthotics. Arch supports, usually prefabricated, have become a popular way to treat pes planus. Most custom orthotics made by taking a mold of the foot will have built-in arch support. In addition, there are special custom shoes that can be made for flat-footed people.
- Exercise and stretching. Stretching the foot and ankle tendons before an activity is important for people with flat feet. Furthermore, for runners with flat feet, the Achille's tendon must be stretched since the Achille's tendon tends to be shorter in flat-footed people.
- Physical therapy. A physical therapist can give specific exercise instructions and use modalities to decrease muscle and tendon tightness, including ultrasound, ice, heat, and electrical stimulation.
- Medications. Medications can only be used for short-term relief, including non-steroidal anti-inflammatories, over-the-counter pain meds like Tylenol, or prescription pain meds like opioids.
- Surgical treatment. Surgery is only considered on rare occasions when there is consistent pain despite the above treatments. In addition, surgery is indicated if there are structural issues needing repair, like a tendon or bone.
How to avoid developing flat feet
There are no specific sports or activities that can prevent the development of flat feet. However, you can limit some risk factors by the following:
- Stay at a healthy weight from exercise and eating healthy — we know obesity can lead to acquired pes planus.
- People with diabetes need to keep their sugars under control.
- Wear properly fitted footwear, especially if you do much walking or standing.
- Try to keep your inflammatory condition (like rheumatoid arthritis) stable.
- Wear quality footwear.
Flat feet is a condition you are born with or acquire during your lifetime. There are some ways to prevent it and other ways to help with the symptoms. However, there is no way to cure the condition completely.