Flatfeet: Causes, Symptoms, and Treatment

Flatfeet is a congenital or acquired foot malposition that occurs very frequently. The longitudinal arch of the foot (from the heel to the ball of the forefoot) sinks due to a weakness of the foot support system. This can cause the heel or forefoot to tilt towards the outer edge.

In extreme cases, the foot can lie completely flat on the ground. A unique form of flat foot is the flat foot. Here the longitudinal arch of the foot only lowers under load.

In contrast to a kinked flatfeet, which is characterized by a similar foot pattern, the flat foot is permanently altered in its shape. It does not straighten up again, even when at rest.

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Causes of the flatfeet

The cause of the development of a flat foot is an abnormal development of the foot skeleton. The healthy foot is arched longitudinally on the inner edge. This means that the foot is usually raised from the ground by about a finger’s breadth. The defective skeleton of the flat foot causes this longitudinal arch to be lowered and the heel to rise.

Depending on the shape of the flat foot, acquired or congenital, the causes of the foot malposition differ. The congenital flat foot (congenital flat foot) is rather rare and usually occurs in combination with other congenital malformations. This form of flat foot is often a family history. This suggests that the flat foot is passed on through generations.

Acquired flatfeet, on the other hand, are mainly caused by an insufficient function of muscles and ligaments.

Reasons for the insufficient function can be permanent overloading, constant standing, overweight, weak connective tissue, or a previous heel fracture. But other diseases such as polio, rickets, neurological or rheumatic diseases can also lead to foot malpositions. These affect the tendons and muscles of the arch of the foot, causing it to lose its efficient support and to sink.

Even constant wearing of shoes can cause a flat foot. Since shoes restrict the freedom of movement of feet and toes and also protect the feet from minor stimuli, the foot muscles are not sufficiently trained and are not strong enough.

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Symptoms of the flatfeet

Usually, symptoms appear on the inner edge of the foot, around the scaphoid, and in the area of the sole.

Sometimes there is also pain in the calves, knees, thighs, and back (see also back pain). The reason for this is the changed load on the entire foot and the resulting unequal distribution of force. If the flat foot is very pronounced, there is usually no more pain.


A flat foot can be detected by only looking at the foot, especially in the case of severe deformities. The footrests much further on the ground than a healthy foot. In some cases, the sole lies flat on the ground. It seems to be rounded off towards the outside (convex), and the tarsal bones are rounded towards the sole.

The Achilles tendon is usually shortened, and the forefoot appears splayed and pulled upwards (dorsally extended). The congenital flat foot shows a steeply positioned ankle bone in the X-ray.

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Stages of the flatfeet

To choose the right therapy for flatfeet, the flat foot can be divided into different stages.

In stage 1, the doctor can passively correct the deformity, and the patient can still actively straighten the longitudinal arch. The Achilles tendon is not yet shortened here.

In stage 2, the foot can still be passively moved into the correct position, but the Achilles tendon is already slightly shortened.

In stage 3, the foot position can only be partially passively corrected, the Achilles tendon is shortened and the rear part of the footpoints outwards.

Severity 4 corresponds in its image to the signs of severity 3, but in addition to the Achilles tendon shortening and the displacement of the rear foot part, there is also a splay of the front foot.

In degree of severity 5, the malposition cannot be corrected. Besides, the heel (rearfoot) is high, and the head of the ankle protrudes at the inner edge of the foot. Also, the forefoot is always splayed. This leads to a lifting of the inner and a lowering of the outer edge of the foot.

Treatment of the flatfeet

In addition to active exercises, the adult foot can only be treated with insoles, as the growth and thus a bony correction is complete.

Flatfeet can only be corrected causally during growth by insoles, exercises, and physiotherapy. Once the growth is complete, one can still try to maintain the situation and achieve freedom from pain. The last option is surgery.

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