What Is Posterior Tibial Tendon Dysfunction (Adult Flatfoot)?

Key takeaways

• PTTD is a leading cause of collapsed arch in adults, usually developing gradually on one side.
• Pain and swelling along the inside of the ankle are the earliest warning signs.
• The condition progresses through recognised stages, from mild tendon irritation to rigid deformity.
• Standard lying-down imaging can miss the alignment changes because the arch relaxes when you are not standing.
• A standing weight-bearing x-ray shows the true position of your bones under load.

What does posterior tibial tendon dysfunction feel like?

The first thing most people notice is a dull ache or swelling along the inside of their ankle, just behind the ankle bone. Walking, especially on uneven ground, makes it worse. Over weeks or months, you may realise your arch looks flatter than it used to, or that one foot points outward more than the other.

A classic clinical clue is the "too many toes" sign. When someone looks at you from behind, more toes are visible on the affected side because the foot has shifted outward. If you are experiencing sudden numbness, weakness, or loss of bladder or bowel control alongside any leg or back pain, seek urgent medical attention from your GP, 111, or A&E rather than booking a scan.

What causes adult acquired flatfoot?

Adult acquired flatfoot develops when the tibialis posterior tendon can no longer hold the arch up under your body weight. Several factors speed this process along.

Your body works as a connected chain. When the arch collapses, the ankle rolls inward (hindfoot valgus), which changes the position of the knee, hip, and even the spine. Pain often shows up somewhere other than the foot itself. Assessing your full lower limb alignment helps explain these knock-on effects.

What are the stages of PTTD?

PTTD is usually described in four stages. Each stage reflects how much the tendon has deteriorated and how far the foot's shape has changed. The earlier it is identified, the more options are available to manage it.

In stages 1 and 2 the foot is still flexible, meaning the shape can be corrected by hand or with support. By stage 3 the joints have stiffened and the deformity is fixed. Stage 4 means the ankle joint itself has begun to tilt. Identifying the stage accurately depends on seeing how the bones sit while you are standing, not while you are lying down on a scanner table.

How is PTTD assessed with standing imaging?

A standing weight-bearing x-ray captures the true position of your foot bones while gravity and your body weight act on them. This is essential because lying-down scans allow the arch to spring back, hiding the real extent of collapse.

What helps manage posterior tibial tendon dysfunction?

Management depends on the stage and severity. ScanAlign is a diagnostic imaging clinic, so we provide the imaging that informs your treatment elsewhere. Here is what your treating clinician may consider.

• Orthotic support and bracing. Custom insoles or an ankle brace can support the arch and reduce strain on the tendon, especially in the earlier stages. Read more about orthotics and overpronation.
• Physiotherapy. Targeted exercises can strengthen the muscles around the foot and ankle to share the load.
• Activity modification. Reducing high-impact activities temporarily allows the tendon to settle.
• Surgery. In later stages, surgical procedures may be discussed to realign the bones or repair the tendon. Accurate staging from weight-bearing images helps surgeons plan the right approach.

Frequently asked questions about PTTD