Adult acquired flatfoot

Adult acquired flatfoot is a gradual flattening of the arch that develops in adulthood. It most often starts when the posterior tibial tendon, which runs along the inner ankle and helps hold up the arch, becomes weakened or damaged. Without that support the arch can slowly collapse and the heel can tilt outward. Specialists also call it progressive collapsing foot deformity.

• Pain and swelling along the inner side of the ankle and arch
• An arch that looks flatter than before, often on one side
• Pain or fatigue with long periods of standing or walking
• Weakness or difficulty rising onto the toes on the affected foot
• A heel that tilts outward, with the toes pointing out more, when seen from behind
• In later stages, pain on the outer side of the ankle

The posterior tibial tendon can weaken from repeated strain over time, from an injury such as a fall, or from arthritis or loose ligaments in the midfoot that overload it. As the tendon and the ligaments supporting the arch stretch or tear, the arch drops further, which puts even more strain on the structures that remain.

It is more common in:

• Women
• Adults over 40
• People with obesity, diabetes, or high blood pressure

Flat feet that have been present since childhood are a different situation and often cause no problems.

A clinician examines both feet while you stand and walk, looking at the arch and the angle of the heel, and checks for tenderness and swelling along the tendon. A single-leg heel rise — standing on one foot and rising onto the toes — helps show whether the tendon is working. The exam also checks whether the foot is still flexible or has become stiff, and how tight the calf is.

Standing X-rays show the foot's alignment and any arthritis. MRI or ultrasound can show the condition of the tendon and ligaments, and a CT scan may be used for more detail, especially when surgery is being planned.

Non-surgical care is the starting point and helps many people:

• Rest from activities that cause pain, and a switch to low-impact exercise
• Ice and anti-inflammatory medication when appropriate, which ease symptoms but do not change the shape of the foot
• Over-the-counter or custom orthotics that support the arch
• A lace-up ankle brace, or a custom brace for more advanced or stiff deformities
• A period in a walking boot or cast for a flare of tendon pain
• Physical therapy to strengthen the tendon and stretch the calf
• Weight loss when appropriate

Steroid injections near the posterior tibial tendon are generally avoided because they can weaken it.

When pain and function do not improve, surgery may be considered. The operation depends on the stage of the condition and whether the foot is flexible or stiff, and several procedures are often combined:

• Removing inflamed tissue around the tendon and repairing small tears
• Transferring a nearby tendon to take over for the damaged posterior tibial tendon
• Repairing stretched ligaments that support the arch
• Cutting and shifting the heel bone (osteotomy) to restore alignment
• Lengthening a tight calf muscle or Achilles tendon
• Fusing stiff or arthritic joints in the back of the foot in advanced cases

Recovery after flatfoot reconstruction is a long process. It generally involves several weeks without putting weight on the foot, then a gradual return to walking in a boot and later in supportive shoes, along with physical therapy. Full recovery often takes many months. Following weight-bearing instructions closely, and managing health factors such as diabetes and smoking, supports healing.

Not every case can be prevented, but these steps may lower the strain on the tendon:

• Maintain a healthy body weight
• Wear supportive shoes, especially for long periods on your feet
• Seek care early for pain along the inner ankle, before the arch changes shape