Home / Conditions / Posterior tibial tendon
The posterior tibial tendon runs behind the bony bump on the inside of the ankle and holds up the arch of the foot. When it weakens, the arch slowly flattens — the commonest cause of a flat foot that develops in adulthood. Often shortened to PTTD, it tends to worsen if left, so it is worth treating early.
Posterior tibial tendonitis in its early stage can look like nothing more than a sore inner ankle. Left alone, it can move through four stages, each changing the shape of the foot a little more — and what helps depends on the stage.
| Stage 1 | Stage 2 | Stage 3 | Stage 4 | |
|---|---|---|---|---|
| What you notice | Pain and swelling behind the inner ankle bone | The arch dropping, and walking tiring quickly | Pain on the outer side as well | The ankle itself painful and tilting |
| How the foot looks | Normal, or mildly flat | Flat on standing; the heel drifts outwards | Flat, and stays that way | Flat, with the ankle tilted |
| Can it be corrected? | Yes | Yes — it is still flexible | No — it has become rigid | No |
| What usually helps | Rest, a boot or brace, then insoles and exercises | Insoles and a brace; surgery to rebuild the tendon if not | A brace, or surgery to fuse the joints | Surgery that includes the ankle |
Flat feet you have always had, on both sides, and that do not hurt, are usually nothing to treat. The pattern to take seriously is an arch that is flattening now, one foot looking different from the other, or pain behind the inner ankle bone. And if the inner ankle gave way with a pop and you can no longer rise onto tiptoe on that foot, the tendon may have torn — call the clinic and come in within a day or two.
The tendon starts from a deep muscle in the calf, curves around behind the bony bump on the inside of the ankle, and attaches under the arch. Every step, it pulls the arch up and helps you rise onto your toes.
What a picture cannot show is why it wears where it does. Just behind that bony bump the tendon bends sharply and its blood supply is poorest, so that is where it weakens. As it does, the arch sags, the heel tips outwards, and the ligaments of the foot are stretched in turn.
That is why it progresses. A sagging arch loads the weakened tendon even more, so each stage makes the next more likely — and why a flexible flat foot is far easier to treat than one that has set rigid.
Treatment depends on the stage. Early on, the aim is to rest the tendon and support the arch so it can recover; later, surgery can rebuild the tendon or correct the shape of the foot.
For a painful, swollen tendon, a few weeks in a supportive boot or brace takes the load off so it can settle. This is the first step of posterior tibial tendonitis treatment, and in stage 1 it is often enough.
An insole that supports the arch, sometimes with an ankle brace, reduces the strain on the tendon. A programme of strengthening exercises then builds it back up. Insoles support the foot rather than reverse the flattening, so they work best early.
When the foot is still flexible but has not settled, the tendon can be reinforced with a neighbouring tendon, and the heel bone realigned to restore the arch. Recovery takes several months, with a period in a cast and then a boot.
Once the foot has set rigid, the joints at the back of the foot are fused in a corrected position — flatfoot reconstruction. It gives a stable, less painful foot, though it stiffens it permanently, which is one reason earlier treatment is preferred.
Posterior tibial tendon dysfunction here is seen by Dr Jeffrey Tan Gek Meng, a Senior Consultant Orthopaedic Surgeon whose subspecialty is foot and ankle, and whose work includes flatfoot reconstruction. He is a Fellow of the Royal College of Surgeons of Edinburgh, completed his subspecialty fellowship in foot and ankle surgery at Toronto Western Hospital, and consults in English, Mandarin, Malay, Hokkien and Hainanese.
No. Many people have flat feet all their lives, on both sides, with no pain, and need no treatment. A flat foot matters when it is new, getting worse, painful, or affecting one foot more than the other.
They describe the same condition at different points. Posterior tibial tendonitis is the painful early stage; PTTD, posterior tibial tendon dysfunction, covers its progression as the arch flattens. In its advanced form it is now often called progressive collapsing foot deformity.
They support the arch and ease the strain on the tendon, which helps a great deal in the early stages. They do not reverse flattening that has already happened, so they work best alongside exercises, and early.
It often does. A weakening tendon lets the arch sag, which strains the tendon further. Treating it while the foot is still flexible usually avoids the larger operations needed once it has set rigid.
Not usually in the early stages. Surgery is considered when a flexible flat foot has not settled with support and exercise, or when the foot has become rigid and painful.
No. Bring any foot X-rays or scan reports, and be ready to say whether one foot has changed shape, and when you first noticed.
Tell us whether one foot has changed shape, and when you first noticed. That usually shows how far it has progressed.
