Differential Diagnosis for Calf Injury

The patient's presentation of a "pop" in the left calf after stepping out of her car, followed by an inability to bear weight with her heel down, suggests a significant injury. The differential diagnosis can be categorized as follows:

• Single Most Likely Diagnosis

  • Achilles Tendon Rupture: This is the most likely diagnosis given the sudden onset of pain and the characteristic "pop" sound, which is often reported by patients who suffer from this injury. The inability to bear weight on the heel is also consistent with an Achilles tendon rupture, as it compromises the patient's ability to plantarflex the foot.

• Other Likely Diagnoses

  • Calf Strain: A strain of the muscles in the calf could also present with sudden pain and potentially a "pop" if severe enough. However, the inability to bear weight with the heel down might be less pronounced compared to an Achilles tendon rupture.
  • Gastrocnemius or Soleus Muscle Tear: Tears in these muscles can mimic the symptoms of an Achilles tendon rupture, including pain and difficulty walking, but might not always include the distinct "pop" sound.

• Do Not Miss Diagnoses

  • Deep Vein Thrombosis (DVT): Although less likely given the acute onset and mechanism of injury, DVT could present with calf pain and swelling. It's crucial to consider DVT, especially if there are risk factors such as recent travel, immobilization, or a history of clotting disorders, as it can be life-threatening if not promptly treated.
  • Compartment Syndrome: This is a serious condition that could result from any significant injury to the calf, including fractures or severe muscle tears. It presents with the 5 Ps: pain, pallor, pulselessness, paresthesia, and poikilothermia. Early diagnosis is critical to prevent long-term damage.

• Rare Diagnoses

  • Plantaris Tendon Rupture: The plantaris muscle and tendon are small and not always present, but when they are, a rupture can mimic an Achilles tendon rupture, including a "pop" sound. However, this is much less common.
  • Popliteal Artery Aneurysm Rupture: Although extremely rare and unlikely without other symptoms such as coldness or discoloration of the foot, a ruptured aneurysm could present with acute calf pain and is a medical emergency.