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What Is Adult Acquired Flatfoot?

Adult Acquired Flatfoot (AAF) occurs when the arch collapses over time due to tendon weakness, ligament stretching, or structural changes in the foot. Most cases begin with Posterior Tibial Tendon Dysfunction (PTTD) — the tendon responsible for supporting the arch.

As the arch collapses, the foot turns outward, causing pain, instability, and difficulty walking.

Common Symptoms

• Flattening of the arch

• Pain along the inside of the ankle

• Foot turning outward

• Swelling or tenderness

• Difficulty standing or walking

• Trouble fitting into shoes

• Progressive deformity over time

Why Adult Flatfoot Happens

AAF often develops due to:

• Posterior Tibial Tendon Dysfunction (PTTD)

• Overuse

• Previous ankle injuries

• Obesity

• Arthritis

• Age‑related tendon degeneration

• High‑impact activity

Without treatment, the deformity can progress and become rigid.

Stages of Adult Flatfoot

Stage 1 — Tendon Inflammation

Pain and swelling along the inner ankle.

Stage 2 — Arch Collapse Begins

The foot starts to flatten; heel shifts outward.

Stage 3 — Rigid Flatfoot

The arch is fully collapsed and no longer flexible.

Stage 4 — Ankle Arthritis

The deformity affects the ankle joint, causing severe pain.

When Adult Flatfoot Becomes a Problem

You should be seen if you experience:

• Daily arch or ankle pain

• A visibly flattening foot

• Difficulty walking

• Pain that worsens with activity

• Swelling on the inside of the ankle

• Trouble standing for long periods

If your arch collapse is causing ankle weakness, it may be related to Ankle Instability.

Treatment Options

At Orthopedic Foot & Ankle Institute, our team — Dr. Sibel, Dr. Samant, Dr. Savage, and Dr. Solomon — offers:

• Custom Orthotics

• Bracing for arch support

• Anti‑inflammatory treatments

• Shockwave therapy (Coming Soon)

• Physical therapy

• PRP injections for chronic tendon damage

For advanced cases, learn more about surgical options on our Reconstructive Surgery page.

Do All Cases of Adult Flatfoot Require Surgery?

Not always. Many patients improve with early conservative care. However, surgery may be recommended if:

• The arch continues to collapse

• Pain persists despite treatment

• The tendon is torn

• The deformity becomes rigid

• Daily activities are limited

Our specialists offer modern flatfoot reconstruction techniques designed to restore alignment and relieve pain.

Schedule an Appointment Today

Call Our Office at 702.997.9833

Author

Roman Sibel, MD Dr. Roman Sibel, MD is an orthopedic surgeon practicing at Orthopedic Foot & Ankle Institute in Henderson, Nevada. Dr. Sibel specializes in a variety of cutting-edge foot and ankle treatments, including reconstructive surgery, sports medicine, trauma surgery, diabetic care, and laser treatments for removing nail fungus. Dr. Sibel retains active affiliations with numerous Las Vegas hospitals, including Southern Hills Hospital and Medical Center, and St. Rose Dominican Hospital’s multiple campuses throughout Nevada. He also works with several local surgical centers, such as Parkway Surgery Center, Sunset Ridge Surgery Center, and Coronado Surgery Center. Graduating from Pennsylvania State University in University Park, Pennsylvania, Dr. Sibel went on to earn his medical degree from MCP-Hahnemann School of Medicine in Philadelphia. He completed both his internship and residency in orthopedic surgery at Ohio State University in Columbus, Ohio, and finished his foot and ankle fellowship training at the Hospital