Can ankle strain lead to pes planus?

Relationship Between Ankle Strain and Pes Planus

Ankle strain alone does not directly cause pes planus (flatfoot), but inadequately treated ankle sprains can lead to chronic problems including decreased range of motion, pain, and joint instability that may contribute to the development of acquired flatfoot in some cases.

Ankle Sprains and Their Consequences

Ankle sprains are among the most common musculoskeletal injuries, accounting for approximately 2 million injuries per year in the United States 1. The most typical mechanism is a lateral ankle inversion sprain that occurs in the plantar-flexed position.

When evaluating the potential relationship between ankle strain and pes planus, it's important to understand:

• Acute ankle injuries primarily affect the lateral stabilizing ligaments (anterior talofibular, calcaneofibular, and posterior talofibular) 1
• Inadequate treatment of ankle sprains can lead to chronic problems including:
  • Decreased range of motion
  • Persistent pain
  • Joint instability 1

Posterior Tibial Tendon Dysfunction (PTTD) - The Critical Link

The posterior tibial tendon (PTT) is the primary dynamic stabilizer of the medial arch of the foot. When examining the relationship between ankle injuries and flatfoot:

• PTTD is the most common cause of acquired pes planus in adults 2
• The posterior tibial tendon functions to:
  • Elevate the arch of the foot
  • Lock midtarsal joints
  • Create rigidity in the midfoot-hindfoot 2
• When the PTT fails to function properly, other foot ligaments and joint capsules progressively weaken, potentially leading to pes planus 2

Risk Factors and Mechanisms

Several factors can contribute to the development of PTTD and subsequent pes planus:

• Age-related tendon degeneration
• Inflammatory arthritis
• Hypertension
• Diabetes mellitus
• Obesity
• Peritendinous injections
• Acute traumatic rupture of the tendon 2

While direct ankle sprains primarily affect lateral ligaments, severe or recurrent ankle trauma may indirectly affect medial structures including the posterior tibial tendon, particularly in cases of:

• High ankle (syndesmotic) sprains that involve dorsiflexion and eversion of the ankle with internal rotation of the tibia 1
• Chronic ankle instability from inadequately treated sprains 1

Diagnostic Considerations

When evaluating a patient with ankle pain and potential flatfoot:

• Flexible pes planus shows a normal arch during non-weight-bearing or tiptoeing, with flattening on standing 3
• Rigid pes planus remains stiff and collapsed regardless of weight-bearing status 3
• MRI is the reference standard for ligamentous injury assessment and can help determine the grade of injury 1
• Radiographs may be indicated based on the Ottawa Ankle Rules to exclude fractures 1

Management Implications

For patients with ankle sprains who may be at risk for developing pes planus:

• Implement the PRICE protocol (Protection, Rest, Ice, Compression, Elevation) for acute ankle injuries 4
• Use semirigid or lace-up ankle supports for functional treatment 1
• Prioritize early controlled weight-bearing and range of motion exercises 4
• Implement a progressive exercise program including:
  • Range of motion exercises
  • Strengthening exercises
  • Proprioceptive training
  • Neuromuscular training 4

Prevention of Chronic Issues

To prevent progression from ankle strain to potential pes planus:

• Ensure complete rehabilitation before returning to full activities 4
• Consider use of semirigid or lace-up ankle supports to decrease risk of recurrent ankle injury, especially in patients with a history of recurrent sprains 1
• Implement graded exercise regimens with proprioceptive elements such as ankle disk training 1
• Monitor for signs of PTTD in patients with persistent medial ankle pain following injury 2

Common Pitfalls to Avoid

• Overlooking fractures (use Ottawa Ankle Rules)
• Prolonged immobilization (which can weaken supporting structures)
• Premature return to activity before adequate healing
• Failing to recognize PTTD as a potential complication of ankle trauma 4

While direct causation between simple ankle strain and pes planus is not established in the literature, understanding the relationship between ankle injuries, posterior tibial tendon dysfunction, and the development of acquired flatfoot is crucial for appropriate management and prevention of long-term complications.