Flatfoot (Pes Planus) and Progressive Collapsing Foot Deformity
Overview
Flatfoot describes a low arch, often with the heel tilted outwards. Painless flexible flatfoot—especially in children—is commonly a normal variation and does not require treatment. In adults, a previously stable foot can become painful and progressively collapse as tendons, ligaments and joints lose support. This is called progressive collapsing foot deformity. Treatment depends on pain, flexibility, arthritis, alignment and cause rather than arch height alone.
Flexible and rigid flatfoot
In a flexible flatfoot, the arch reappears when sitting, standing on tiptoe or lifting the big toe. A rigid flatfoot remains flat and has limited side-to-side movement at the heel. A painful, stiff, newly developing or markedly asymmetric flatfoot should be assessed because tarsal coalition, arthritis, a nerve or muscle condition, or another structural problem may be present.
In children, painless flexible flatfoot is usually a normal variation. Treatment is not needed simply to create an arch. Orthoses may improve comfort but do not permanently reshape the bones. New pain, stiffness, asymmetry, frequent sprains or loss of function should be reviewed.
Progressive collapsing foot deformity in adults
Adult collapse may involve the posterior tibial tendon, spring ligament, hindfoot, midfoot and sometimes the ankle. The heel tilts outwards, the forefoot drifts outwards and the arch lowers. Calf tightness, inflammatory disease, previous injury, diabetes, age-related tissue change and increased load on the supporting structures can contribute.
Pain may occur along the inner ankle and arch, under the outer ankle from impingement, or through arthritic joints. Weakness or inability to perform a single-leg heel rise can reflect loss of posterior tibial tendon function.
Assessment and imaging
Assessment is performed standing and walking and includes heel alignment, arch, forefoot position, flexibility, calf tightness, tendon strength and areas of tenderness. Both feet are compared, and the ankle is assessed for outward tilt or arthritis.
Weight-bearing foot and ankle X-rays are central to assessment. A hindfoot alignment view, ultrasound or MRI for tendon and ligament disease, and CT for coalition, arthritis or complex deformity may be added when relevant.
Non-surgical treatment
- Supportive footwear and avoidance of worn, unstable shoes.
- An insole (orthosis) for a flexible deformity or an ankle-foot brace for more advanced or rigid symptoms.
- A progressive program for calf flexibility, posterior tibial tendon and whole-limb strength, balance and walking control.
- Temporary load reduction and a short period in a Moonboot for a painful tendon flare in selected cases.
- Support with weight and general health optimisation when relevant to your health and goals.
- Pain-relieving or anti-inflammatory medicine after checking that it is suitable for your health and current medicines.
When may surgery be considered?
Surgery may be discussed when pain or progressive deformity continues to cause major limitations despite appropriate bracing and rehabilitation. The foot must be classified as flexible or rigid and each component of collapse identified. There is no single ‘flatfoot operation’.
A flexible deformity may require a combination of controlled bone cuts in the heel or midfoot, tendon repair or transfer, ligament reconstruction, selective fusion and calf-lengthening. A rigid or arthritic deformity more often requires fusion of selected joints in the back or middle of the foot. Outward ankle tilt or ankle arthritis can require additional treatment.
Recovery
Reconstruction commonly requires a prolonged period of protected or non-weight-bearing followed by staged loading in a cast or Moonboot. Bone procedures and tendon or ligament healing determine progression. Swelling, strength and walking endurance improve over many months.
Insoles or supportive footwear may still be useful after surgery. The aim is a more comfortable, stable foot that rests more evenly on the ground—not a perfectly shaped arch or normal movement in every case.
Risks and limitations
- Wound problems, infection, blood clots or medical complications.
- Nerve irritation, numbness or painful hardware.
- Delayed or failed bone healing, or loss of correction.
- Persistent pain, stiffness, weakness or residual deformity.
- Over-correction, under-correction or lateral foot overload.
- Progression of arthritis and need for further surgery.
Frequently asked questions
Does every flat foot need treatment?
No. Painless flexible flatfoot, particularly in children, usually requires reassurance rather than treatment.
Can orthotics rebuild the arch?
They can support the foot and reduce symptoms but do not permanently change adult bone shape.
Is posterior tibial tendon dysfunction the same as flatfoot?
It is one important contributor to adult progressive collapse, but ligaments, joints and the ankle may also be involved.
Why are weight-bearing X-rays important?
The deformity and joint alignment can appear very different when the foot is loaded.
Is fusion always required?
No. Flexible deformities may be reconstructed with controlled bone cuts and soft-tissue procedures. Fusion is more often used when the foot is rigid or arthritic.
General information
This page provides general information only. It cannot diagnose your condition or replace advice from a clinician who has assessed you. Your treatment and recovery plan may differ from the examples described here. Follow the instructions from your treating team. In an emergency, call 000 or attend the nearest emergency department.