What Is Posterior Tibial Tendon Dysfunction (Adult Flat Foot)?
Posterior tibial tendon dysfunction (PTTD) is a condition that gets worse over time. The tendon that supports the arch of your foot weakens or tears. Slowly, the arch drops and the foot rolls inward. This causes pain on the inside of the ankle. It is the most common cause of flat foot that develops in adults. It is best checked with weight-bearing imaging.
Key takeaways
- PTTD is a leading cause of a collapsed arch in adults. It usually develops slowly, on one side.
- Pain and swelling along the inside of the ankle are the earliest warning signs.
- The condition passes through known stages, from mild irritation of the tendon to a rigid deformity.
- Usual scans done lying down can miss the changes in alignment, 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?
Most people first notice a dull ache or swelling along the inside of the ankle, just behind the ankle bone. Walking makes it worse, especially on uneven ground. Over weeks or months, you may see that your arch looks flatter than before. Or one foot may point outward more than the other.
A classic clinical clue is the "too many toes" sign. When someone looks at you from behind, they see more toes on the affected side, because the foot has shifted outward. If you have sudden numbness, weakness, or loss of bladder or bowel control along with any leg or back pain, get urgent medical help from your doctor or the nearest emergency department rather than booking a scan.
What causes adult acquired flat foot?
Adult acquired flat foot develops when the tibialis posterior tendon can no longer hold the arch up under your body weight. Several factors speed this up.
Your body works as a connected chain. When the arch collapses, the ankle rolls inward (hindfoot valgus). This changes the position of the knee, the hip and even the spine. Pain often shows up somewhere other than the foot itself. Checking 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 shows how much the tendon has worn down and how far the shape of the foot has changed. The earlier it is found, the more options there are to manage it.
In stages 1 and 2 the foot is still flexible. This means its 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 started to tilt. Finding the stage accurately depends on seeing how the bones sit while you stand, not while you lie on a scanner table.
How is PTTD checked with a standing scan?
A standing weight-bearing X-ray shows the true position of your foot bones while gravity and your body weight act on them. This is essential. Scans done lying down let the arch spring back, which hides how far it has really collapsed.
Shows the arch under real load. With your full body weight pressing through the foot, the image shows exactly how much the arch has dropped, how far the heel has tilted, and whether nearby joints have shifted. This is how clinicians stage PTTD accurately.
At ScanAlign, weight-bearing standing imaging captures your feet, ankles, knees and hips in a single standing exposure, with about 90% less radiation than a standard X-ray, around ten times less. This means your clinician can see the full chain reaction, not just one joint on its own.
Misses what gravity shows. When you lie flat, your muscles relax and the arch lifts slightly. The image may look almost normal even when the foot collapses a lot as you stand or walk. This can make the stage of PTTD look milder than it is and delay the right management.
When is MRI the better choice? EOS shows bones, joints and alignment very clearly. For soft tissue detail, such as the state of the tendon itself, any tears, or inflammation around it, MRI is usually the better tool. Your clinician may recommend both.
What helps manage posterior tibial tendon dysfunction?
Management depends on the stage and how severe it is. ScanAlign is a diagnostic imaging clinic. We provide the imaging that guides 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 so they share the load.
- Changing your activity. Cutting back on high-impact activities for a while lets the tendon settle.
- Surgery. In later stages, surgery may be discussed to realign the bones or repair the tendon. Accurate staging from weight-bearing images helps surgeons plan the right approach.
Before you start treatment, or change the one you are on, it is worth getting a detailed diagnosis. Knowing whether the cause sits in the pelvis, the legs or the spine changes what will actually help.
If you have ongoing pain on the inside of the ankle, an arch that is flattening, or you have been told you have adult flat foot, clear imaging of your foot alignment under load is an important first step.
Book a free video consultationFrequently asked questions about PTTD
Not exactly. Many people have flat feet from childhood and never have problems. PTTD is a condition that gets worse over time. The tendon weakens, and the arch collapses in adulthood. It usually affects one foot and gets worse without management.
If someone looks at you from behind, they can normally see your little toe, and perhaps the one next to it, peeking out beside the ankle. With PTTD the foot shifts outward, so three or four toes can be seen on the affected side. It is a simple visual check that clinicians use.
PTTD is a progressive condition. This means it tends to get worse rather than better without treatment. Early support, such as orthotics and physiotherapy, can slow or stop it getting worse. That is why accurate staging matters.
When you lie down, gravity no longer pushes on your arch, so it may look more normal than it really is. A standing weight-bearing image shows how the bones actually sit when you are upright and carrying your full body weight. This gives a more accurate picture of the deformity.
Yes. The EOS system uses about 90% less radiation than a standard X-ray, around ten times less. It captures your full alignment in a single standing image, so there is no need for several separate exposures.
No. You can refer yourself. The process starts with a free video consultation. A specialist radiographer reviews your situation and confirms whether a standing scan is right for you.
You can book a weight-bearing foot scan, starting with a free video consultation. The price for patients travelling from abroad is confirmed during this free video consultation.
Yes. When your arch collapses, the ankle rolls inward. This changes how forces travel up through the knee, hip and spine. Pain or stiffness in those areas can sometimes be traced back to a problem with foot alignment. A full lower limb alignment assessment helps join the dots.
Tibialis posterior tendinopathy means early damage or inflammation inside the tendon. PTTD describes the wider progressive condition. This includes the changes to the structure of the foot that follow if the tendon keeps weakening. Tendinopathy is often seen as the earliest part of the PTTD spectrum.
Orthotics support the arch and reduce symptoms. But they do not reverse structural changes that have already happened. In earlier stages they can be very effective at preventing further collapse. Your clinician will advise you based on your imaging and examination findings.
Understand your foot alignment under real load
The first step is a free video consultation with a specialist radiographer, wherever you live. No referral needed, no obligation.
Book a free video consultationWritten by Abbas Dhami (Specialist Diagnostic Radiographer)
Sources
- Myerson MS. Adult acquired flat foot deformity: treatment of dysfunction of the posterior tibial tendon. Journal of Bone and Joint Surgery (American). 1996;78(5):780-792.
- NHS. Flat feet. nhs.uk. Available at: https://www.nhs.uk/conditions/flat-feet/
- Kohls-Gatzoulis J, Angel JC, Singh D, Haddad F, Livingstone J, Berry G. Tibialis posterior dysfunction: a common and treatable cause of adult acquired flatfoot. BMJ. 2004;329(7478):1328-1333.
This page is general information and not a diagnosis.
ScanAlign is the trading name of CoreMed Solutions Ltd and operates under The Harley Street Hospital's CQC licence.