PatientPlus articles are written by UK doctors and are based on research evidence, UK and European Guidelines. They are designed for health professionals to use, so you may find the language more technical than the condition leaflets.
Synonyms: planovalgus foot
Pes planus (PP) is the loss of the medial longitudinal arch of the foot. There are various types and causes of flat feet. Usually, treatment is only needed if PP is new, painful or progressing, or when there is a fixed deformity or other associated problem.
The flat arch does not occur in isolation, but affects the dynamics of the foot. So, patients standing on a flat foot will usually have:
- Valgus position of the heel (turned outwards).
- Pronation of the midfoot, usually referred to as 'hyperpronation' (the midfoot turns inwards).
- Valgus (turned out) position of the forefoot.
Note: the definition refers to the foot bones, not the soft tissues. People with hypertrophied plantar foot muscles (eg lifelong barefoot walkers) might appear to have flat feet, when their bony arches are normal.
Types of PP
PP may be:
- Developmental or acquired
- Flexible or fixed
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- Pes planus (PP) can be part of normal development:
- Infants typically have a minimal arch.
- Many toddlers have flattening of the long arch, with forefoot pronation and heel valgus on weight-bearing.
- There may be ligamentous laxity, which is probably determined genetically.
- Most of these children spontaneously develop a strong normal arch by around age 10.
- Abnormal development of the foot, producing PP, may be due to:
- Physiological PP:
- There is a lack of normal arch development, probably due to inherent ligamentous laxity.
- Around 20% of adults have PP. The majority have a flexible flat foot and no symptoms. However, if there is also heel cord contracture, there may be symptoms (see 'Contributing factors', below).
- Adult-acquired PP - causes:
- Loss of support for the arch:
- Dysfunction of the tibialis posterior tendon - a common and important cause.
- Tear of the spring ligament (rare).
- Tibialis anterior rupture (rare).
- A neuropathic foot, e.g from diabetes, polio, or other neuropathies.
- Degenerative changes in foot and ankle joints:
- Inflammatory arthropathy, eg rheumatoid arthritis.
- Bony abnormalities, eg tarsal coalition.
- Loss of support for the arch:
- Footwear: shoes which limit toe movement; high heels. Barefoot walking may be protective.
- A tight Achilles tendon or calf muscles (heel cord contracture). This may help to cause PP, or may contribute to symptoms such as foot pain when there is existing PP.
- Other bony abnormalities, eg rotational deformities, tibial abnormalities, coalition (fusion) of tarsal bones, equinus deformity.
- Ligamentous laxity, eg familial, Marfan's syndrome, Ehlers-Danlos syndrome, Down's syndrome.
- Other factors causing foot pronation, eg hip abductor weakness and genu valgum.
Presentation and assessment
Patients may present with noticeable pes planus (PP), parental concerns, or foot pain.
- History of the PP and any changes.
- Symptoms: walking/running ability and any foot pain.
- Past medical history: other diseases, developmental delay.
- Is the PP new? Is it symmetrical?
- Is there foot pain or interference with walking?
- Are there any other lower limb symptoms, eg knee pain?
- Past medical history: injuries, other related disease (neurological, rheumatological, musculoskeletal).
- Occupation and hobbies.
- If PP is new, asymmetrical or painful, ask about symptoms of tibialis posterior dysfunction, which are:
- Pain or swelling behind the medial malleolus and along the instep.
- Change in foot shape.
- Decreasing walking ability and balance.
- Ache on walking long distances.
- Observe the PP.
- With the patient standing, look at his or her feet from above and behind. Loss of the arch is visible, with the medial side of the foot close to the ground. Look at the feet from behind - with PP the heel moves outwards (valgus) and the toes may also be pointed outwards.
- Is the PP flexible?
- Ask the patient to stand on tiptoe. With flexible PP, this will reveal the arch, and the heel will move inwards (varus position).
- Look for signs of tibialis posterior dysfunction (if history is suggestive of this):
- Ask the patient to do 10 unsupported heel raises (stand on one foot on tiptoe, unsupported). Patients with tibialis posterior dysfunction will be unable to do this.
- Further assessment of tibialis posterior dysfunction is detailed in the reference below.
- Assess related problems, if relevant, eg neuropathy or arthritis.
In some cases, standing foot X-rays may be used to show the degree of deformity:
- Standing lateral view shows the longitudinal arch and talonavicular joint.
- Standing AP view shows the degree of heel valgus (talocalcaneal angle).
Is treatment necessary?
In many cases, pes planus (PP) does not require treatment:
- The arch may develop spontaneously in children under 10 years with flexible PP and no other relevant condition.
- In adults, a 'good' PP is one which has has been present a long time, is flexible, bilateral, painless, and not progressing.
Consider referral or treatment for PP if:
- PP is fixed, new, asymmetrical, progressing, there is foot pain, or if the patient has another disease which may be contributing (eg neuropathy or inflammatory arthritis).
- There is tibialis posterior dysfunction. This should be treated in its own right: treatment may involve rest, non-steroidal anti-inflammatory drugs (NSAIDs), orthotics or surgery.
- Heel cord stretching is an important part of treatment, as a tight Achilles tendon tends to pronate the foot. See box for details.
- Orthotics (inserts or insoles, often custom-made) may be used. These usually contain a heel wedge to correct calcaneovalgus deformity, and an arch support.
- This is the usual treatment for flexible PP (if treatment is needed).
- A suitable insole can help to correct the deformity while it is worn. Possibly it may prevent progression of PP, or may reduce symptoms. However, the effectiveness of arch support insoles is uncertain.
- Note: arch supports used without correcting heel cord contracture can make symptoms worse.
- In patients with fixed PP or arthropathy, customised insoles may relieve symptoms.
- Reduce contributing factors:
- Wear shoes with low heels and wide toes.
- Lose weight if appropriate.
- Do exercises to strengthen foot muscles - walking barefoot (if appropriate), toe curls (flexing toes) and heel raises (standing on tiptoe).
Heel cord stretching exercisesThese stretch and lengthen the Achilles tendon and posterior calf muscles.
- Stand facing a wall with your hands on the wall at about eye level. Put the leg you want to stretch about a step behind your other leg.
- Keeping your back heel on the floor, bend your front knee until you feel a stretch in the back leg.
- Hold the stretch for 15-30 seconds. Repeat 2-4 times.
- Do this exercise 3-4 times a day.
Common indications for surgery are:
- Cerebral palsy with an equinovalgus foot, to prevent progression and breakdown of the midfoot.
- Rigid and painful PP.
- To prevent progression, eg with a Charcot joint.
- Tibialis posterior dysfunction, where non-surgical treatment is unsuccessful.
Possible surgical procedures include:
- Achilles tendon lengthening.
- Calcaneal osteotomy, to re-align the hindfoot.
- Reconstruction of the tibialis posterior tendon.
- For severe midfoot collapse of the arch, triple arthrodesis may be indicated.
Complications and prognosis
Physiological pes planus (PP)
It is generally stated that physiological PP is unlikely to cause significant foot problems. However, some authors suggest that excessive foot pronation (which usually occurs with PP) may contribute to the development of foot pain and foot problems such as:
- Tibialis posterior dysfunction (because hyperpronation stretches this tendon).
- Hallux valgus (because more weight is borne by the medial metatarsals when the foot hyperpronates).
- Metatarsalgia (for the same reason).
- Plantar fasciitis.
- Knee pain: one study found that off-the-shelf foot orthoses were beneficial for patellofemoral pain. Another study suggested that foot deformity may be linked to greater disability from knee osteoarthritis.
- PP may reduce the shock-absorbing features of the foot, potentially contributing to low back pain.
The role of PP in these problems has not been proved.
Other types of PP
Depending on the cause, PP can deteriorate, with loss of the longitudinal arch leading to collapse of the midfoot. With deterioration, a flexible PP can become rigid and/or painful. This can cause significant difficulties with walking and may require surgery.
Situations where deterioration is likely without treatment include:
Further reading & references
- Richie DH Jr; Biomechanics and clinical analysis of the adult acquired flatfoot. Clin Podiatr Med Surg. 2007 Oct;24(4):617-44, vii.
- Jacobs AM; Soft tissue procedures for the stabilization of medial arch pathology in the management of flexible flatfoot deformity. Clin Podiatr Med Surg. 2007 Oct;24(4):657-65, vii-viii.
- Kadakia AR, Haddad SL; Hindfoot arthrodesis for the adult acquired flat foot. Foot Ankle Clin. 2003 Sep;8(3):569-94, x.
- Flat foot, The Foot and Ankle Clinic (2008); private orthopaedic clinic website; contains clinical information and pictures for patients and clinicians
- Hyperpronation and foot pain, the physician and sportsmedicine 32;8 (August 2004)
- Pes planus/flat foot; Wheeless' Textbook of Orthopaedics, detailed information on paediatric and adult condition with resources and images
- Kohls-Gatzoulis J, Angel JC, Singh D, et al; Tibialis posterior dysfunction: a common and treatable cause of adult acquired flatfoot. BMJ. 2004 Dec 4;329(7478):1328-33.
- Napolitano C, Walsh S, Mahoney L, et al; Risk factors that may adversely modify the natural history of the pediatric pronated foot. Clin Podiatr Med Surg. 2000 Jul;17(3):397-417.
- Kulcu DG, Yavuzer G, Sarmer S, et al; Immediate effects of silicone insoles on gait pattern in patients with flexible flatfoot. Foot Ankle Int. 2007 Oct;28(10):1053-6.
- Esterman A, Pilotto L; Foot shape and its effect on functioning in Royal Australian Air Force recruits. Part 2: Pilot, randomized, controlled trial of orthotics in recruits with flat feet. Mil Med. 2005 Jul;170(7):629-33.
- Collins N, Crossley K, Beller E, et al; Foot orthoses and physiotherapy in the treatment of patellofemoral pain syndrome: randomised clinical trial. BMJ. 2008 Oct 24;337:a1735. doi: 10.1136/bmj.a1735.
- Guler H, Karazincir S, Turhanoglu AD, et al; Effect of coexisting foot deformity on disability in women with knee osteoarthritis. J Am Podiatr Med Assoc. 2009 Jan-Feb;99(1):23-7.
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Dr Naomi Hartree
Dr Richard Draper
Dr Helen Huins