Posterior Tibial Tendon Dysfunction

Posterior tibial tendon dysfunction (PTTD) — also called adult-acquired flatfoot — is the gradual failure of a tendon that runs along the inside of your ankle and holds up the arch of your foot. As the tendon weakens, stretches out, and eventually tears through, the arch on the inside of your foot flattens, your heel angles outward, and your forefoot drifts toward the outside. Looking at the foot from behind, you can see extra toes peeking out on the outside (the classic too-many-toes sign).

It's most common in women over 40, people carrying extra weight, anyone with high blood pressure or diabetes, and people whose work has them on hard floors all day.

• Pain along the inside of the ankle and arch — an aching or burning that starts behind the inner ankle bone and runs along the inside of the foot.
• Arch flattening on one side — you notice one foot is becoming flatter than the other, and your old shoes start wearing unevenly.
• Can't rise onto tiptoes on the affected foot — standing on one leg, you either can't push up onto your toes at all or the heel doesn't swing inward like it should.
• Heel drifting outward — looking at your feet from behind, extra toes peek out on the outside of the affected foot (the "too-many-toes sign").
• Fatigue and aching after standing or walking — the inside of your ankle and foot tire quickly and throb after time on your feet.

The key exam test is the single-leg heel rise — your provider asks you to stand on the affected foot and rise up onto your tiptoes. With a working tendon, your heel angles inward as you rise. With PTTD, you usually can't rise onto your tiptoes at all on that side, or the heel doesn't swing inward like it should. Standing X-rays of the foot from three angles measure how much the arch has collapsed and how far the heel has drifted outward. An MRI shows how badly the tendon itself has degenerated. Your provider stages the disease I through IV, and the stage drives treatment.

Surgery is for early-stage disease that hasn't responded to bracing and rehab, and for the more advanced stages where the arch has collapsed too far for braces alone to hold. The operation usually combines a tendon transfer (using a healthy nearby tendon to take over) with bony cuts that reshape the foot's alignment.

External patient-education references and related OSI pages for additional background:

• Britannica — Ankle (anatomy)
• AAOS OrthoInfo — patient education library
• OSI glossary — orthopedic terminology in plain language