Reviewed by Kevin L. Kirk, D.O., F.A.O.A.
Flat feet can occur for many reasons, and not everyone with a low or flattened arch experiences pain. Some people have flexible flat feet from childhood and remain active without limitations. Others develop a progressively collapsing arch as adults because the posterior tibial tendon, the tendon that helps support the arch and control foot movement—becomes stretched, inflamed, weakened, or torn.
This condition is commonly known as adult-acquired flatfoot deformity or posterior tibial tendon dysfunction (PTTD). The American Orthopaedic Foot & Ankle Society (AOFAS) also describes this condition as progressive collapsing foot deformity. Without appropriate evaluation and treatment, the foot may gradually lose its arch, roll inward, and become painful or unstable.
At TSAOG Orthopaedics and Spine Foot & Ankle Institute’s experienced foot and ankle surgeons can evaluate painful or progressive flatfoot and recommend treatment based on the condition’s severity, cause, and effect on your daily activities.
What Is Adult-Acquired Flatfoot?
Adult-acquired flatfoot occurs when the arch gradually collapses after it previously developed normally. One of the most common causes is dysfunction of the posterior tibial tendon.
The posterior tibial tendon runs along the inside of the ankle and attaches to bones in the foot. It helps support the arch and assists with turning the foot inward while walking. When the tendon becomes damaged or stops functioning properly, the arch may gradually flatten, and the heel may shift outward.
This can change the alignment of the entire foot. In addition to tendon dysfunction, the ligaments and joints that support the arch may also become strained or damaged over time.
Adult-acquired flatfoot is different from the flexible flat feet that many people have since childhood. It is more likely to progress and cause pain, weakness, instability, or difficulty walking.
What Causes Posterior Tibial Tendon Dysfunction?
Posterior tibial tendon dysfunction may result from gradual wear and tear, overuse, an injury, or conditions that place additional stress on the foot. Risk factors may include:
- Increasing age, particularly after age 40
- Being overweight or obese
- Diabetes
- High blood pressure
- Previous ankle or foot injuries
- Repetitive walking, standing, or high-impact activity
- Inflammatory conditions such as rheumatoid arthritis
- A naturally flat or poorly aligned foot
The condition is more common in women and in adults over 40, although it can affect anyone.
What Are the Symptoms of Adult-Acquired Flatfoot?
Symptoms may develop gradually and become more noticeable with prolonged standing, walking, or physical activity. Common signs include:
- Pain or tenderness along the inside of the ankle or arch
- Swelling along the posterior tibial tendon
- A flattening or loss of the arch
- The heel shifting outward
- The foot rolling inward while standing or walking
- Weakness when trying to stand on the toes
- Difficulty walking on uneven ground
- Reduced balance or foot stability
- Fatigue in the foot or leg
- Pain that worsens with activity and improves with rest
- A change in shoe fit or uneven shoe wear
As the condition progresses, pain may spread to the outside of the ankle or the top and middle portions of the foot. Some patients eventually develop stiffness or arthritis in the joints of the hindfoot.
A simple sign of posterior tibial tendon dysfunction is difficulty performing a single-leg heel raise. A patient may be unable to rise onto the toes of the affected foot or may experience pain and weakness while attempting to do so.
How Is Adult-Acquired Flatfoot Diagnosed?
Diagnosis begins with a medical history and physical examination. A foot and ankle surgeon may assess:
- The shape of the arch while standing and sitting
- Foot and ankle alignment
- Tenderness or swelling along the posterior tibial tendon
- The ability to perform a heel raise
- Strength and range of motion
- Walking pattern and balance
- Flexibility or stiffness in the foot
- Signs of arthritis or other structural problems
Weight-bearing X-rays may be recommended because they show how the bones and joints align while the foot is supporting the body. Additional imaging, such as magnetic resonance imaging (MRI), may be useful when the condition of the posterior tibial tendon or other soft tissues needs further evaluation.
An accurate diagnosis helps determine whether the flatfoot is flexible or rigid and whether the deformity is primarily related to tendon dysfunction, arthritis, injury, or another cause.
How Does Posterior Tibial Tendon Dysfunction Progress?
Adult-acquired flatfoot may progress through several phases. Early in the condition, the tendon may be inflamed or weakened, but the arch may still be maintained. As dysfunction progresses, the arch can collapse and the heel can move outward. Over time, the foot may become less flexible, and arthritis or significant deformity may develop.
The severity and flexibility of the deformity influence treatment. Early evaluation is important because nonsurgical care is generally most effective before the foot becomes rigid or substantial joint damage occurs.
What Treatments Are Available for Adult-Acquired Flatfoot?
Treatment depends on the severity of symptoms, the condition of the tendon, the flexibility of the foot, and whether arthritis or other deformity is present.
Nonsurgical Treatment
Many patients initially improve with a combination of conservative treatments, such as:
- Supportive shoes with a firm heel counter
- Over-the-counter or custom orthotics
- An ankle-foot orthosis or other supportive brace
- Temporary immobilization in a walking boot
- Activity modification
- Ice and elevation for swelling
- Physical therapy
- Exercises to improve calf flexibility, balance, and tendon function
- Weight management when appropriate
- Anti-inflammatory medication when recommended by a healthcare professional
Orthotics and braces may help support the arch and reduce stress on the posterior tibial tendon. Physical therapy can improve strength and flexibility, but exercises should be selected by a qualified professional because the appropriate program depends on the severity of the condition.
Surgical Treatment
Surgery may be considered when pain and functional limitations continue despite appropriate nonsurgical treatment or when significant deformity develops.
The specific procedure depends on the structures involved. Surgical treatment may include removing the diseased posterior tibial tendon and tendon transfer, lengthening a tight calf or Achilles tendon, realigning the heel or other bones, repairing supporting ligaments, or addressing arthritis in damaged joints.
The goals of surgery are to reduce pain, improve alignment, restore stability, and preserve or improve foot function. Not every patient requires surgery, and treatment should be individualized after a thorough examination and discussion of expected benefits and risks.
When Should You See a Foot and Ankle Specialist?
A low arch does not automatically require treatment. However, evaluation is recommended when you notice:
- New or worsening pain along the inside of the ankle or arch
- Swelling around the ankle
- A recently flattened arch
- A change in the position of the heel
- Difficulty standing on one foot or rising onto the toes
- Increasing difficulty walking or exercising
- Foot or ankle symptoms that do not improve with rest and supportive shoes
Early assessment may help identify posterior tibial tendon dysfunction before the deformity becomes more difficult to manage.
Adult-Acquired Flatfoot Treatment at TSAOG Orthopaedics & Spine
Flat feet are not always painful, but a newly flattened or progressively changing arch in an adult may be a sign of posterior tibial tendon dysfunction. Prompt evaluation can help distinguish a stable, flexible flatfoot from a progressive collapsing foot deformity.
TSAOG’s Foot & Ankle specialists provide individualized care for adults and children with flatfoot conditions. Treatment recommendations are based on your symptoms, physical examination, imaging findings, activity level, and long-term goals.
If pain, swelling, changes in foot shape, or difficulty with daily activities are affecting you, schedule an appointment with TSAOG to learn more about your condition and treatment options.
This information is for educational purposes only and is not a substitute for professional medical evaluation or treatment.
References
- American Orthopaedic Foot & Ankle Society, FootCareMD. Adult-Acquired Flatfoot Deformity:
https://www.footcaremd.org/foot-and-ankle-conditions/midfoot/adult-acquired-flatfoot-deformity - Harvard Health Publishing. Fallen Arch: A to Z:
https://www.health.harvard.edu/diseases-and-conditions/fallen-arch-a-to-z - Henry JK, et al. Adult-Acquired Flatfoot Deformity:
https://pmc.ncbi.nlm.nih.gov/articles/PMC8696898/ - Medical News Today. Flat Feet:
https://www.medicalnewstoday.com/articles/320383
