Differential Diagnosis for Ankle Injury

Given the information provided, the following differential diagnoses can be considered:

• Single Most Likely Diagnosis

  • Ankle sprain: This is the most common injury in the ankle and can cause soft tissue edema and joint effusion without an apparent fracture or dislocation. The fact that MRI is more sensitive for internal derangement supports this diagnosis, as sprains can involve ligamentous injuries that may not be visible on initial X-rays.

• Other Likely Diagnoses

  • Ligamentous injury (e.g., deltoid ligament or syndesmotic injury): These injuries can occur with or without a fracture and may present with similar findings, including soft tissue edema and joint effusion.
  • Tendinosis or tendonitis: Conditions affecting the tendons around the ankle, such as Achilles tendonitis or peroneal tendinosis, can cause swelling and pain without an acute fracture or dislocation.
  • Osteochondral lesion: An injury to the cartilage and bone of the ankle joint, which might not be immediately visible on X-rays but could cause joint effusion and pain.

• Do Not Miss Diagnoses

  • Compartment syndrome: Although less likely, compartment syndrome is a serious condition that requires immediate attention. It can present with swelling and pain out of proportion to the injury and can lead to serious complications if not promptly treated.
  • Infection (e.g., cellulitis or septic arthritis): Infections can cause swelling, redness, and pain. While less common in the context of an acute ankle injury without a clear entry point for infection, they are critical to diagnose early to prevent serious complications.

• Rare Diagnoses

  • Stress fracture: A small, incomplete fracture in the bone that might not be visible on initial X-rays. Stress fractures can cause pain and swelling but are less common in the acute setting described.
  • Neuroma or nerve entrapment: Conditions affecting the nerves around the ankle, which could cause pain and swelling but are less directly related to the acute trauma scenario described.
  • Soft tissue tumor: Extremely rare in the context of an acute injury, but could potentially cause swelling and should be considered if other diagnoses are ruled out and symptoms persist.