Differential Diagnosis for Left Ankle Pain
Given the symptoms of left ankle pain over the Anterior Talofibular Ligament (ATFL), pain to the lateral malleolus, and radiation up the fibula, with no history of injury and normal ultrasound and X-ray findings, the following differential diagnoses are considered:
Single Most Likely Diagnosis
- Peroneal Tendinopathy: This condition involves inflammation of the peroneal tendons, which run along the lateral aspect of the ankle and behind the lateral malleolus, matching the area of pain described. The absence of a history of injury does not rule out this diagnosis, as repetitive strain or overuse can cause tendinopathy.
Other Likely Diagnoses
- Lateral Ankle Impingement: This condition can cause pain on the lateral side of the ankle, similar to the symptoms described. It might not always show abnormalities on X-ray or ultrasound, especially if it's related to soft tissue or dynamic issues.
- Fibular Stress Reaction or Stress Fracture: Although X-rays are often normal in early stress fractures, the pain pattern described could fit a stress reaction or fracture of the fibula, especially if the patient has recently increased their activity level.
- ATFL Strain or Sprain without Significant Injury: Even without a clear history of injury, minor strains or sprains can occur and cause pain over the ATFL.
Do Not Miss Diagnoses
- Osteoid Osteoma: A small, benign bone tumor that can cause severe pain, often worse at night, and may not be visible on initial X-rays. It's crucial to consider this diagnosis due to its potential for significant morbidity if left untreated.
- Ewing's Sarcoma or Other Malignancies: Although rare, these conditions can present with pain and may not have obvious findings on initial imaging. Given the potential severity, they must be considered in the differential diagnosis.
- Infection (Osteomyelitis or Septic Arthritis): Infections can cause pain and may not always have clear findings on initial imaging, especially in early stages. They are medical emergencies and must be ruled out.
Rare Diagnoses
- Nerve Entrapment (Superficial Peroneal Nerve): This can cause pain and symptoms along the lateral aspect of the leg and ankle but is less common.
- Ganglion Cyst: A lump or mass that can cause pain if it presses on nearby nerves, though it's less likely given the description of pain without a palpable mass.
- Haglund's Deformity: More commonly associated with posterior heel pain, but in rare cases, could contribute to lateral ankle pain if there's associated peroneal tendon irritation.