What is Adult Acquired Flatfoot?

Adult Acquired Flatfoot, also known as Posterior Tibial Tendon Dysfunction (PTTD), is a progressive condition where the arch of the foot collapses over time. Unlike congenital flatfoot (present from childhood), this condition develops in adulthood, most often due to weakening or tearing of the posterior tibial tendon—a key structure that supports the arch and stabilizes the foot. As the tendon fails, the arch flattens, the heel shifts outward, and the foot may become painful and unstable.

Causes

Adult Acquired Flatfoot most commonly results from:

  • Posterior tibial tendon degeneration or injury (the leading cause)

  • Overuse or repetitive stress on the tendon

  • Underlying conditions such as obesity, diabetes, hypertension, or inflammatory arthritis

  • Previous foot injuries or fractures

  • Pre‑existing flatfoot that worsens with age

  • Ligament failure (spring ligament, deltoid ligament) contributing to arch collapse

Symptoms

Patients with Adult Acquired Flatfoot may notice:

  • Pain and swelling along the inside of the ankle or arch

  • Flattening of the arch that worsens over time

  • Heel drifting outward and forefoot turning outward (“too many toes” sign when viewed from behind)

  • Difficulty standing on tiptoe or pushing off when walking

  • Pain on the outside of the ankle in later stages, due to joint impingement

  • Trouble walking long distances, climbing stairs, or wearing certain shoes

Diagnosis

Diagnosis typically involves:

  • Physical exam – checking arch height, heel alignment, and ability to perform a single‑leg heel rise

  • Observation of gait – looking for outward drift of the foot or collapse of the arch

  • Imaging – weight‑bearing X‑rays to assess deformity; MRI or ultrasound if tendon damage needs to be evaluated

  • Staging – the condition is classified into four stages, from early tendon inflammation (Stage I) to rigid deformity with ankle arthritis (Stage IV)

Nonsurgical Treatment

In early stages, nonsurgical care can relieve symptoms and slow progression:

  • Custom orthotics or ankle braces to support the arch and reduce strain

  • Immobilization in a boot or cast during acute pain flares

  • Physical therapy to strengthen supporting muscles and improve flexibility

  • Anti‑inflammatory medications to reduce pain and swelling

  • Activity modification to avoid high‑impact stress on the tendon

  • Weight management to reduce pressure on the foot

When is Surgery Needed?

Surgery may be recommended when:

  • Pain persists despite 3–6 months of nonsurgical treatment

  • The deformity continues to worsen, leading to instability or difficulty walking

  • The foot becomes rigid and cannot be corrected manually

  • Arthritis develops in the hindfoot or ankle joints

Surgical options vary by stage and may include tendon repair or transfer, bone realignment (osteotomy), ligament reconstruction, or joint fusion in advanced cases. The goal is to restore alignment, relieve pain, and preserve mobility.