Pes planus (Flat feet)

Overview

Flat feet are said to be present when the arches on the inside of the feet are flattened, allowing the entire soles of the feet to touch the floor on standing. It is important to realise that it is only relevant in the weight bearing or the standing position. Most people with flexible flat feet will recover their arches when they are not weight bearing. 

It is a common and usually painless condition. It can occur when the arches don't develop during childhood (congenital or physiological). In other cases, flatfeet develop after an injury (traumatic) or from the simple wear-and-tear stresses of age (degenerative). Flatfeet can contribute to problems in the ankles and knees because the condition can alter the alignment of the legs. Nevertheless, no treatment is usually necessary for flatfeet if there is no pain. Most people have no signs or symptoms associated with flatfeet. But some people with flatfeet experience foot pain, particularly in the heel or arch area. Pain may worsen with activity. Swelling along the inside of the ankle can also occur.



Figure 1. Typical abnormalities seen in flat feet. The forefoot usually splays outwards and the medial arch is collapsed. From the back the heel is out (valgus) and there are 'too many toes' seen.

Causes

A flat foot is normal in infants and toddlers, because the foot's arch hasn't yet developed. Most people's arches develop throughout childhood, but some people never develop arches. This is a normal variation in foot type, and people without arches may or may not have problems. Some children have flexible flatfoot, in which the arch is visible when the child is sitting or standing on tiptoes, but disappears when the child stands. Most children outgrow flexible flatfoot without problems. Arches may fall over time. Years of wear and tear can weaken the tendon that runs along the inside of your ankle and helps support your arch.

Figure 2. In addition to the loss of arches best appreciated from the side, the foot becomes wider resulting in difficulty in finding appropriate shoes.

Factors that can worsen flat feet include

  1. Obesity - the increased weight increases the downward forces on the foot
  2. Injury to your foot or ankle - especially tendon injuries
  3. Rheumatoid arthritis - ligaments and tendons here are generally weak
  4. Aging - tendons can undergo degenerative tears
  5. Diabetes - predisposes to tendon rupture


Figure 3. As the midfoot arch fails it causes pressure on the nerves and tendons at the sole of the feet and may be responsible for increased pain

Diagnosis

To view the mechanics of the feet, they are observed from the front and back both on the flat and standing on toes. The wear pattern on shoes is a useful clue. We have an entire article on wear patterns in shoes here .

 

Imaging tests

Ordinarily, xrays and scans of the feet are not necessary. Nevertheless, if there is a lot of pain in the feet or in the case of the child who hasn't outgrown the condition by puberty, further imaging may be necessary.



Figure 4. Xrays are usually done to identify bony abnormalities and not to confirm the presence of flatfeet. As a result they are usually not required.
  1. X-rays. A simple X-ray uses a small amount of radiation to produce images of the bones and joints in your feet. It's particularly useful in detecting arthritis. In children there can be clues to bones that are out of alignment or that failed to separate along the course of normal development.
  2. CT scan. This test takes X-rays of your foot from different angles and provides much more detail than a standard X-ray. They are only usually resorted to in specific cases of painful causes of flat-feet like tarsal coalitions where the bones are fused together.
  3. Ultrasound.When an injured tendon is suspected this test test is done. It uses sound waves to produce detailed images of soft tissues within the body.
  4. MRI. This test is usually done to look closely at tendons to see if they have become torn or are likely to.
  5. Gait analysis. Our clinic offers 2 cutting edge systems involving motion capture analysis and forceplate arrays at coming to a sound understanding of the kinetics of motion of the feet in relation to the body.

Treatment

No treatment is necessary for flatfeet if they don't cause pain or they do not cause secondary deformities to the knee and ankle.

The first line of therapy usually involves: 

  1. Over-the-counter arch supports may help relieve the pain caused by flatfeet. Or your doctor might suggest custom-designed arch supports, which are molded to the contours of your feet. Arch supports won't cure flatfeet, but they often reduce symptoms.
  2. Stretching exercises are relevant to some people with flatfeet who also have a shortened Achilles tendon. Exercises to stretch this tendon may help.
  3. A structurally supportive shoe might be more comfortable than sandals or shoes with minimal support.
  4. Flatfeet may contribute to overuse injuries in some runners. A physical therapist can do a video analysis of how you run to help you improve your form and technique.

Surgery isn't done solely to correct flatfeet. However, you might have surgery for an associated problem, such as a tendon tear or rupture.


Figure 5. This child with persistent flatfeet into puberty had a subluxed  subtalar joint. This was treated with a minimally invasive procedure involving subtalar distraction through a 2 cm incision which healed well.


Figure 6. The same child seen from the side whose arches were restored.


Figure 7. A middle aged adult with bunions and a hypermobile first ray who underwent correction and was able to return to running afterwards.