Differential Diagnosis for Ankle Injury

The patient presents with a 2-week history of ankle pain and swelling on the lateral aspect after rolling her ankle, which hurts when walking. Here's a categorized differential diagnosis:

• Single Most Likely Diagnosis

  • Ankle Sprain: This is the most common injury when someone rolls their ankle. The lateral aspect of the ankle is frequently affected due to the mechanism of injury, which often involves inversion of the foot. The symptoms of pain, swelling, and difficulty walking are consistent with a sprain, particularly of the anterior talofibular ligament.

• Other Likely Diagnoses

  • Ankle Fracture: While less common than a sprain, a fracture could occur, especially if the mechanism of injury was severe or if the patient has osteoporosis. The presence of swelling and pain, especially with weight-bearing, could suggest a fracture.
  • Peroneal Tendon Injury: The peroneal tendons run along the lateral aspect of the ankle and can be injured in ankle sprains. Symptoms might include pain and swelling along the tendon paths and difficulty with ankle stability.
  • Ligamentous Laxity or Chronic Ankle Instability: If the patient has a history of repeated ankle sprains, they might develop chronic instability, characterized by a feeling of the ankle "giving way" and persistent pain.

• Do Not Miss Diagnoses

  • Compartment Syndrome: Although rare, compartment syndrome is a medical emergency that can occur after an ankle injury. It involves increased pressure within the muscle compartments, leading to severe pain, pallor, poikilothermia, paresthesia, and pulselessness. Early diagnosis and treatment are crucial to prevent long-term damage.
  • Osteochondral Lesion of the Talus: This condition involves a piece of cartilage and bone in the talus (ankle bone) becoming damaged or detached. It can cause chronic pain and swelling and might not be immediately apparent after an ankle injury.
  • Infection (e.g., Cellulitis or Abscess): If the skin was broken during the injury, there's a risk of infection. Signs might include increasing redness, warmth, swelling, and fever.

• Rare Diagnoses

  • Stress Fracture: A stress fracture could occur, especially in athletes or individuals with repetitive stress on the ankle bones. Symptoms might include gradual onset of pain that worsens with activity.
  • Neuroma: A neuroma, such as a Morton's neuroma, could cause pain in the foot or ankle, although it's less directly related to an acute ankle sprain.
  • Gout or Pseudogout: These conditions involve deposition of urate or pyrophosphate crystals within the joints, leading to acute inflammatory arthritis. While they can affect the ankle, they are less common causes of pain following a sprain.