Adult Acquired Flatfoot Deformity (AAFD) is a progressive condition that causes the collapse of the medial arch of the foot, leading to significant pain, deformity, and difficulty walking. Unlike congenital flatfoot, which is present from birth, AAFD develops over time and is most often seen in middle-aged and older adults, particularly women.
How Common It Is and Who Gets It? (Epidemiology)
AAFD is most common in middle-aged and older adults, especially women. The condition often develops as a result of degeneration of the posterior tibial tendon (PTT), which helps maintain the foot’s arch. Other factors, such as obesity, diabetes, hypertension, rheumatoid arthritis, and the use of steroids, increase the risk of developing this condition. Those with pre-existing flexible flatfoot or other foot abnormalities are also at an elevated risk.
Why It Happens – Causes (Etiology and Pathophysiology)
The most common cause of AAFD is degeneration of the posterior tibial tendon (PTT), which leads to the collapse of the foot’s medial arch. Over time, the tendon can stretch, weaken, or rupture, causing the foot to lose its normal structure. As the condition progresses, other stabilizing structures, such as the spring ligament, deltoid ligament, and plantar fascia, may also fail, further contributing to deformity. Factors like obesity, diabetes, and previous injuries increase the likelihood of developing AAFD.
How the Body Part Normally Works? (Relevant Anatomy)
The foot contains 26 bones, 30 joints, and numerous tendons and ligaments that work together to provide support and movement. The posterior tibial tendon (PTT) is a key structure in maintaining the foot’s arch. It runs behind the medial malleolus and attaches to the bones of the foot, including the navicular. The PTT lifts the arch and stabilizes the foot during walking. Other ligaments, including the spring ligament and deltoid ligament, also support the arch. When these structures fail, the foot collapses inward and the arch flattens.
What You Might Feel – Symptoms (Clinical Presentation)
Symptoms of AAFD vary depending on the stage of the condition:
- Pain and swelling along the inside of the ankle, especially in the early stages
- Flattening of the arch
- Difficulty standing on tiptoe
- Outward drifting of the foot as the deformity progresses
- Pain along the outer ankle or foot in later stages
- Ankle instability and difficulty with balance
One characteristic sign of AAFD is the “too many toes” sign—when viewed from behind, more than two toes may be visible on the outside of the foot due to forefoot drifting outward.
How Doctors Find the Problem? (Diagnosis and Imaging)
Diagnosis is made through a combination of physical examination and imaging:
- Clinical Examination: Includes assessment of arch height, the “too many toes” sign, and the single-limb heel raise test. The doctor may also check for changes in foot shape and flexibility.
- X-rays: Show bone alignment and joint uncoverage, which is helpful in determining deformity severity.
- MRI: Provides detailed images of soft tissues, such as tendons and ligaments, helping assess the extent of tendon damage and ligament failure.
- CT scans (weight-bearing): Useful for surgical planning and evaluating joint subluxation when the patient is standing.
- Ultrasound: Can assess the posterior tibial tendon for inflammation or tears.
Classification
AAFD is classified into four stages:
- Stage I: Mild inflammation or degeneration of the posterior tibial tendon without deformity. The foot remains flexible, and the patient can perform a single-limb heel raise.
- Stage II: The foot begins to deform but remains flexible. The patient may lose the ability to invert the heel during a heel raise.
- Stage IIA: Less than 30% talonavicular joint uncoverage.
- Stage IIB: More than 30% uncoverage, indicating more severe deformity.
- Stage III: The deformity becomes rigid, and arthritis may begin to set in.
- Stage IV: The deformity extends to the ankle joint, often with deltoid ligament failure, leading to arthritis and significant instability.
Other Problems That Can Feel Similar (Differential Diagnosis)
Several conditions can mimic the symptoms of AAFD, including:
- Posterior tibial tendon tears
- Arthritis of the ankle joint
- Subtalar joint instability
- Peroneal tendonitis
- Rheumatoid arthritis
Clinical testing and imaging help differentiate AAFD from these other conditions.
Treatment Options
Non-Surgical Care
Non-surgical treatments are effective, particularly in the early stages:
- Custom orthotics or braces (e.g., UCBL insert, Arizona brace)
- Anti-inflammatory medications to reduce pain and swelling
- Immobilization using a boot or cast for acute pain
- Physical therapy focusing on strengthening the foot and ankle, improving flexibility, and restoring balance
- Activity modification to reduce stress on the foot
In cases of early Stage II, orthotics combined with physical therapy show significant success in improving symptoms.
Surgical Care
Surgery is considered if non-surgical treatments fail or if the deformity progresses. Surgical options include:
- Medializing calcaneal osteotomy (MCO): Repositions the heel bone to correct alignment.
- Gastrocnemius recession or Achilles lengthening: Reduces tightness in the calf muscles.
- Lateral column lengthening (LCL): Lengthens the outer side of the foot to restore alignment.
- Spring ligament reconstruction: Rebuilds critical support for the medial arch.
- Tendon transfer: Replaces the posterior tibial tendon with another tendon, such as the flexor digitorum longus.
- Triple arthrodesis: Fuses the subtalar, talonavicular, and calcaneocuboid joints to create a stable foot.
Recovery and What to Expect After Treatment
- Non-surgical recovery: Symptoms usually improve within 6–8 weeks with proper treatment. Patients are advised to follow a structured rehabilitation plan to strengthen the foot and reduce pain.
- Surgical recovery: After surgery, recovery typically takes 3–6 months, depending on the type of procedure performed. Early mobility is crucial for rehabilitation, and patients may be required to undergo physical therapy.
Possible Risks or Side Effects (Complications)
- Recurrence of pain if the underlying issues are not fully addressed.
- Nonunion: Failure of the bones to heal together after surgery.
- Infection: As with all surgeries, there is a risk of infection.
- Nerve damage: Rare, but possible, especially during surgery.
Long-Term Outlook (Prognosis)
With early diagnosis and appropriate treatment, the prognosis for AAFD is generally good. Most patients experience relief from pain and improvement in function. Surgery offers good outcomes for more severe cases, although full recovery may take several months. After surgery, patients can usually return to normal activities, though high-impact sports may be restricted.
Out-of-Pocket Costs
Medicare
CPT Code 28300 – Calcaneal Osteotomy (for Adult Acquired Flatfoot Deformity): $153.01
Medicare Part B typically covers 80% of the approved cost for this procedure once your annual deductible has been met, leaving you responsible for the remaining 20%. Supplemental Insurance plans, such as Medigap, AARP, or Blue Cross Blue Shield, typically cover the remaining 20%, reducing or eliminating out-of-pocket expenses for Medicare-approved surgeries. These plans work with Medicare to fill the coverage gap.
If you have Secondary Insurance such as TRICARE, an Employer-Based Plan, or Veterans Health Administration coverage, it acts as a secondary payer. These plans typically cover any remaining balance, including coinsurance or small deductibles, which generally range from $100 to $300 depending on your plan and provider network.
Workers’ Compensation
If your adult acquired flatfoot deformity is related to a work-related injury, Workers’ Compensation will cover all treatment costs, including surgery and rehabilitation. You will not have any out-of-pocket expenses, as the employer’s insurance carrier covers all costs directly.
No-Fault Insurance
If your flatfoot deformity is related to an automobile accident, No-Fault Insurance will typically cover the full cost of treatment, including surgery and follow-up care. The only potential out-of-pocket cost may be a small deductible or co-payment based on your policy.
Example
Sarah Williams required a calcaneal osteotomy (CPT 28300) for her adult acquired flatfoot deformity, with an estimated Medicare out-of-pocket cost of $153.01. Since Sarah had supplemental insurance through AARP Medigap, her remaining balance was fully covered, leaving her with no out-of-pocket expenses for the procedure.
Frequently Asked Questions (FAQ)
Q. What is Adult Acquired Flatfoot Deformity (AAFD)?
A. Adult Acquired Flatfoot Deformity is a condition characterized by the progressive collapse of the arch of the foot in adults, most commonly due to dysfunction of the posterior tibial tendon.
Q. What causes Adult Acquired Flatfoot Deformity?
A. The most common cause is posterior tibial tendon dysfunction, but it can also result from trauma, arthritis, or neurologic conditions.
Q. Who is at risk for developing Adult Acquired Flatfoot Deformity?
A. Middle-aged women, individuals with diabetes, obesity, or hypertension, and those with inflammatory arthritis are at increased risk.
Q. What are the symptoms of Adult Acquired Flatfoot Deformity?
A. Symptoms include pain along the inside of the ankle or foot, flattening of the arch, rolling in of the ankle, and difficulty walking or standing for long periods.
Q. How is Adult Acquired Flatfoot Deformity diagnosed?
A. Diagnosis is based on physical examination and imaging studies such as X-rays, MRI, or ultrasound to assess the condition of the tendon and foot alignment.
Q. What are the stages of Adult Acquired Flatfoot Deformity?
A. The condition is classified into four stages, from mild tendon dysfunction without deformity (Stage I) to a rigid flatfoot with arthritis in surrounding joints (Stage IV).
Q. What nonsurgical treatments are available for Adult Acquired Flatfoot Deformity?
A. Nonsurgical options include rest, orthotics, bracing, physical therapy, anti-inflammatory medications, and activity modification.
Q. When is surgery recommended for Adult Acquired Flatfoot Deformity?
A. Surgery is considered when conservative treatment fails to relieve symptoms or when the deformity becomes severe and affects mobility.
Q. What types of surgeries are used to treat Adult Acquired Flatfoot Deformity?
A. Surgical options may include tendon repair or transfer, osteotomies to realign bones, joint fusions, or combination procedures based on the stage and severity.
Q. What is the recovery like after surgery for Adult Acquired Flatfoot Deformity?
A. Recovery typically involves a period of non-weight bearing followed by gradual rehabilitation and physical therapy to restore strength and function.
Q. Can Adult Acquired Flatfoot Deformity be prevented?
A. Early intervention and treatment of posterior tibial tendon dysfunction, along with weight management and avoiding excessive strain on the feet, may help prevent progression.
Summary and Takeaway
AAFD is a progressive condition that causes the collapse of the medial arch in the foot. It can be managed with non-surgical treatments in the early stages, while more severe cases may require surgery. The prognosis is generally favorable with appropriate treatment.
Clinical Insight & Recent Findings
A 2023 review published in Diagnostics emphasizes how imaging plays a central role in diagnosing and managing Adult Acquired Flatfoot Deformity (AAFD). The study highlights that while standard weight-bearing X-rays remain the gold standard for identifying arch collapse and alignment changes, advanced imaging such as MRI, ultrasound, and weight-bearing CT (WBCT) provide critical insight into soft-tissue involvement and deformity severity.
MRI offers precise visualization of posterior tibial tendon and ligament injuries, whereas WBCT delivers three-dimensional, real-weight-bearing evaluation essential for accurate staging and surgical planning.
The authors conclude that these evolving imaging tools improve diagnostic precision and postoperative assessment, paving the way for more tailored, anatomy-guided treatments for patients with progressive flatfoot deformity. (“Study on advanced imaging techniques for adult flatfoot – see PubMed.”)
Who Performs This Treatment? (Specialists and Team Involved)
Treatment is typically managed by orthopedic foot and ankle surgeons. A multidisciplinary team including physical therapists and podiatrists may be involved in rehabilitation.
When to See a Specialist?
Consult a specialist if you experience persistent pain or instability in the foot, particularly if there is difficulty walking or standing for extended periods.
When to Go to the Emergency Room?
Go to the emergency room if you experience severe pain, inability to move the foot, or if you suspect fracture or dislocation.
What Recovery Really Looks Like?
Recovery involves rehabilitation to restore strength and function. Most patients recover fully within 3–6 months, depending on the severity of the condition and the type of treatment.
What Happens If You Ignore It?
If left untreated, AAFD can lead to further deformity, pain, and joint instability, resulting in significant functional limitations and potential arthritis.
How to Prevent It?
Early intervention of posterior tibial tendon dysfunction, weight management, and avoiding excessive strain on the foot can help prevent AAFD progression.
Nutrition and Bone or Joint Health
A healthy diet rich in calcium, vitamin D, and omega-3 fatty acids supports tendon and bone health, reducing inflammation and promoting healing.
Activity and Lifestyle Modifications
Once healed, focus on strengthening the ankle and improving flexibility to prevent recurrence. Avoid high-impact activities until fully recovered.
Dr. Mo Athar
