Magnetic resonance imaging (MRI) arthrography of the ankle is a useful diagnostic modality in the detection and staging of lateral ankle ligament tears, particularly in patients who fail to respond to conservative management. MRI arthrography also may be helpful in determining the extent of ligamentous injury in professional athletes, for whom immediate surgical repair may be the initial treatment. Preoperative planning is optimized with MRI arthrography. Frequently, alternative diagnoses may be made for conditions that can simulate lateral ligamentous injury, thus obviating the need for diagnostic arthroscopy.