Flatfoot vs. PTTD: What’s the Difference?
If you’ve been researching foot pain, you’ve likely encountered both flatfoot and PTTD (posterior tibial tendon dysfunction). These terms are related but not interchangeable. Understanding the difference is important for getting the right treatment.
Quick Answer
Flatfoot (pes planus) is a broad term describing feet with low or no arches. PTTD is a specific condition that causes the arch to collapse, resulting in a flatfoot deformity.
In simple terms: All PTTD is flatfoot, but not all flatfoot is PTTD.
What Is Flatfoot?
Flatfoot is a structural condition where the arch of the foot is flattened, making the entire sole touch the ground when standing.
Types of Flatfoot
1. Flexible Flatfoot
- The most common type
- Arch is present when not bearing weight
- Arch disappears when standing
- Usually present from childhood
- Often asymptomatic
2. Rigid Flatfoot
- No arch present, even when not bearing weight
- Often due to congenital conditions
- May have limited mobility
- More likely to cause symptoms
3. Adult-Acquired Flatfoot
- Develops in adulthood
- Usually due to posterior tibial tendon dysfunction
- Often progresses over time
- Frequently symptomatic
Causes of Flatfoot (Not PTTD)
- Congenital: Present from birth
- Genetics: Inherited foot structure
- Ligament laxity: Loose connective tissue
- Tarsal coalition: Bone fusion in the foot
- Neuromuscular conditions: Cerebral palsy, muscular dystrophy
What Is PTTD?
Posterior tibial tendon dysfunction (PTTD) is a specific condition where the posterior tibial tendon becomes damaged, weakened, or inflamed, causing it to lose its ability to support the arch.
Key Points About PTTD
- It’s a progressive condition
- It’s a cause of adult-acquired flatfoot
- It’s not the same as being born with flat feet
- It worsens over time if untreated
The Mechanics of PTTD
The posterior tibial tendon normally:
- Supports the arch during standing
- Helps invert the foot (turn inward)
- Stabilizes the ankle during walking
- Assists with push-off
When this tendon fails, the arch collapses, creating a flatfoot deformity.
How to Tell the Difference
Here’s how to distinguish between general flatfoot and PTTD:
Onset
| Flatfoot | PTTD |
|---|---|
| Usually present from childhood | Develops in adulthood |
| Gradual if acquired | Often has a more defined onset |
| May be stable over time | Progresses and worsens |
Symptoms
| Flatfoot | PTTD |
|---|---|
| Often asymptomatic | Usually painful |
| May have no discomfort | Pain behind medial malleolus |
| No specific tenderness | Specific tender point |
| Stable condition | Progressive condition |
Age of Onset
| Flatfoot | PTTD |
|---|---|
| Present in childhood | Typically age 40-60 |
| Family history common | Often follows specific trigger |
Activity Related
| Flatfoot | PTTD |
|---|---|
| May not change with activity | Pain worsens with activity |
| Usually doesn’t cause fatigue | Causes significant fatigue |
| Often bilateral (both feet) | May start in one foot |
The Connection: When Flatfoot Is PTTD
Here’s where it gets nuanced:
PTTD Causes Flatfoot
When PTTD develops, it causes the arch to fall, resulting in flatfoot. This is called adult-acquired flatfoot or posterior tibial tendon dysfunction-related flatfoot.
Characteristics of PTTD-Related Flatfoot
- Starts in one foot (usually)
- Progresses over months to years
- Associated with pain
- Often has a specific cause
- Can be staged (Stage 1-4)
When Flatfoot Is NOT PTTD
You have flatfoot that’s NOT PTTD if:
- You’ve had flat feet your whole life
- Both feet are affected equally
- There’s no pain or tenderness
- The condition is stable
- There’s no specific tendon dysfunction
Diagnosing: Is It Just Flatfoot or Is It PTTD?
A healthcare professional can determine the difference through:
Medical History
- When did the flatfoot develop?
- Is it one foot or both?
- Is there pain? Where?
- What makes it better or worse?
Physical Examination
- Checking for tendon tenderness
- Testing strength
- Evaluating arch collapse
- Assessing foot flexibility
Imaging
- X-rays: Show bone alignment and arthritis
- MRI: Shows tendon damage
- Ultrasound: Shows tendon tears and inflammation
Treatment: Different Approaches
Treatment for Asymptomatic Flatfoot
Usually no treatment needed:
- Observation
- Supportive footwear
- Orthotics if desired for comfort
- No intervention required if not causing problems
Treatment for PTTD (Adult-Acquired Flatfoot)
More aggressive treatment is needed:
Conservative Treatment
-
Activity Modification
- Reduce high-impact activities
- Cross-train
-
Physical Therapy
- Eccentric exercises
- Strengthening
- Gait training
-
Orthotics
- Custom arch supports
- Motion-control shoes
-
Medications
- NSAIDs for pain/inflammation
-
Bracing
- Ankle braces
- UCBL orthotics
Surgical Treatment (if needed)
- Tendon repair or transfer
- Osteotomy (bone realignment)
- Fusion procedures
Risk Factors: Who’s More Likely to Get PTTD?
You’re at higher risk for PTTD if you:
- Are between ages 40-60
- Are female
- Have flat feet (biomechanical predisposition)
- Are overweight
- Have diabetes
- Have had previous foot/ankle injuries
- Do high-impact activities
When to Worry About Flatfoot
Not all flatfoot requires treatment, but you should see a doctor if:
- Flatfoot developed recently (in adulthood)
- One foot is flatter than the other
- There’s pain in the feet, ankles, or legs
- You notice changes in your feet
- You’re having balance problems
- Shoes wear unevenly
- You’re limiting activities due to foot discomfort
Can You Have Flatfoot Without PTTD?
Absolutely. Many people with flat feet live perfectly normal, active lives without any pain or dysfunction. The key differentiator is whether the flatfoot is:
- Congenital (you were born with it) vs. acquired (it developed later)
- Stable (not changing) vs. progressive (getting worse)
- Painful (suggesting pathology) vs. asymptomatic (no issues)
Summary: Flatfoot vs. PTTD
| Feature | Flatfoot | PTTD |
|---|---|---|
| Definition | Low or absent arch | Tendon dysfunction causing arch collapse |
| Onset | Usually childhood | Adulthood |
| Causes | Congenital, genetic | Tendon damage, overuse |
| Symptoms | Usually none | Pain, weakness |
| Progression | Usually stable | Gets worse over time |
| Treatment | Often none needed | Active treatment required |
| Usually affects | Both feet | One foot initially |
Conclusion
While flatfoot and PTTD are related, they are distinct conditions:
- Flatfoot is a structural characteristic—the shape of your foot
- PTTD is a dysfunction—a problem with how the tendon works
If you have flat feet but no pain or symptoms, there’s likely nothing to worry about. However, if you’ve noticed recent changes—a new flatfoot, pain, weakness, or instability—it’s worth seeing a healthcare professional to rule out PTTD.
Early detection and treatment of PTTD offers the best outcomes. Don’t ignore new foot pain or changes in your arch.
Experiencing pain specifically behind your ankle bone? Learn about: Why Does My Ankle Hurt Behind My Medial Malleolus?