Flatfoot is very common: 45% of children and 25% of adults have flatfoot. In children younger than 10 years of age it is mostly completely normal, owing to incomplete muscle development and more fat padding on the soles of the feet. Flatfoot itself is not a medical disease; it is simply a description of the shape of the foot. However flatfoot might be hiding other problems.

Flatfoot can be classified into flexible or rigid types.

Flexible flatfoot is the most common. The arches disappear with weight on the feet, with the heels angled outwards, away from the midline. When standing on tiptoe, the heels angle inwards, towards the midline. The image above represents a person with flexible flatfoot. Flexible flatfoot is OK and there is no need to worry about it.

A person with rigid flatfoot has no arches with heel rise, and the heels remain locked angled outwards, away from the midline. Rigid flatfoot might mean that there is a significant problem with the foot mechanism.

Most adolescents with flatfoot and painful feet have flexible flatfoot – the cause of the foot pain is often from tight Achilles tendons, which they cannot see or appreciate. Tight Achilles tendons mostly occur from lack of physical exercise or stretching.

The commonest cause of foot pain, in general, is as a result of lifestyle problems (generalised deconditioning followed by sudden increase in activity, such as sudden increase in walking distance on vacation with incorrect shoes). Therefore, the early treatment of spontaneous foot pain, even in people with flatfoot, is:

• strengthen the foot

• stretch the calf muscles

• wear correct normal shoes with good support

• keep body weight controlled

In general, insoles or "medical shoes" do not significantly benefit flexible adult flatfoot. The medical evidence is that exercise is much better than insoles or medical shoes.  The evidence is here (clickable link). Note in the conclusion of the linked article how the exercise is always part of the winning formula, however insoles and medical shoes can be on the losing side of treatment. ("Exercise alone or combined with foot orthoses showed a better effect on adult flatfoot than only wearing foot orthoses."). The best exercise is Standing Calf Raise to stretch the Achilles and strengthen the muscles of the foot and ankle, and is shown here(clickable link). 

“Medical shoes” can be a visible marker of disability and can therefore do more harm than good in otherwise healthy young adults.

Furthermore, rigid flatfoot does not change its shape even with insoles, and often hurt because of the insoles. 

Flatfoot does not routinely need to be referred to Orthopaedics for treatment.
The correct reasons for referral to Orthopaedics include:

• rigid flatfoot.

• if the flatfoot only starts to develop in adulthood, in a previously normal shape – especially if it changes shape relative to the opposite side

• post-traumatic flatfoot

• if there is strong pain (e.g. unable to perform heel rise)