Does an ankle sprain include an Achilles tendon rupture?

Ankle Sprain vs. Achilles Tendon Rupture

No, an ankle sprain does not include Achilles tendon rupture; they are distinct injuries with different anatomical structures involved, diagnostic criteria, and treatment approaches. 1, 2

Anatomical Differences

• Ankle Sprain:

  • Involves damage to the ligaments that support the ankle joint
  • Most commonly affects lateral ligaments (anterior talofibular, calcaneofibular, and posterior talofibular) 1
  • Typically occurs through an inversion injury in the plantar-flexed position 1

• Achilles Tendon Rupture:

  • Involves a tear in the Achilles tendon (the thickest and strongest tendon in the body)
  • Connects the calf muscles to the calcaneus (heel bone)
  • Typically occurs during high-velocity sports activities 3

Diagnostic Differentiation

Clinical Assessment

• Ankle Sprain Signs:

  • Pain and swelling around the ankle joint, particularly laterally
  • Possible hematoma around the lateral malleolus
  • Positive anterior drawer test (84% sensitivity, 96% specificity when performed 4-5 days post-injury) 1
  • Graded as I (mild), II (moderate), or III (severe) based on injury severity 1

• Achilles Tendon Rupture Signs:

  • Sudden snap or pop sensation in the back of the ankle/calf
  • Difficulty or inability to plantarflex the foot
  • Palpable gap in the tendon
  • Positive Thompson test (squeezing the calf fails to produce foot plantarflexion)
  • Often misdiagnosed as an ankle sprain (up to 20% of cases) 3

Imaging

• For Ankle Sprains:

  • Ottawa Ankle Rules should be applied to determine need for X-rays 1, 2
  • Ultrasound may be used to assess ligament integrity (92% sensitivity, 64% specificity) 1
  • MRI reserved for suspected high-grade ligament injuries or persistent symptoms 1

• For Achilles Tendon Rupture:

  • Ultrasound is highly accurate (94.8% sensitivity, 98.7% specificity) 3
  • MRI may be used for confirmation or surgical planning

Treatment Approaches

• Ankle Sprain Management:

  • PRICE protocol (Protection, Rest, Ice, Compression, Elevation) 2
  • Early functional rehabilitation preferred over immobilization 1
  • Semirigid or lace-up supports recommended 1, 2
  • Progressive strengthening and proprioceptive exercises 2

• Achilles Tendon Rupture Management:

  • Requires either surgical repair or specific conservative treatment with immobilization 4
  • Longer recovery period
  • More structured rehabilitation protocol
  • Higher risk of long-term functional limitations 4

Common Pitfalls

1. Misdiagnosis: Achilles tendon ruptures are frequently misdiagnosed as ankle sprains, leading to inappropriate treatment and poorer outcomes 3, 5

2. Inadequate Examination: Failing to specifically test for Achilles tendon integrity when evaluating ankle injuries

3. Delayed Treatment: Delayed diagnosis of Achilles tendon rupture can lead to more complicated treatment and poorer functional outcomes 5

4. Improper Imaging: Relying solely on X-rays, which cannot visualize soft tissue injuries like tendon ruptures

Clinical Algorithm for Differentiation

1. Location of Pain/Swelling:

   • Lateral ankle → Consider ankle sprain
   • Posterior ankle/lower calf → Consider Achilles pathology

2. Mechanism of Injury:

   • Inversion/eversion → Likely ankle sprain
   • Sudden push-off or direct trauma to tendon → Consider Achilles rupture

3. Specific Tests:

   • Perform anterior drawer test for ankle sprain
   • Perform Thompson test for Achilles rupture
   • Check for palpable gap in Achilles tendon

4. When to Suspect Achilles Rupture Despite Initial Ankle Sprain Diagnosis:

   • Inability to stand on tiptoes
   • Weakness in plantarflexion
   • Pain and swelling in the Achilles tendon area 1
   • Positive Thompson test

Remember that proper differentiation is crucial as treatment approaches differ significantly, and misdiagnosis can lead to poor outcomes and prolonged disability.