Differential Diagnosis
- Single most likely diagnosis
- Ankle sprain: The presence of an abnormal ATFL with heterogeneous fiber morphology and small bone fragments at the fibular insertion, consistent with a bony avulsion injury, along with moderate diffuse thickening and heterogeneity of the CFL, indicates a significant ligamentous injury consistent with an ankle sprain. The additional findings of post-traumatic tenosynovitis of the peroneus longus and mild subcutaneous edema adjacent to the lateral malleolus further support this diagnosis.
- Other Likely diagnoses
- Lateral ankle impingement: The presence of a bony avulsion injury at the ATFL and thickening of the CFL could lead to chronic inflammation and scarring, potentially causing lateral ankle impingement.
- Peroneal tendonitis: The mild tenosynovial fluid around the peroneus longus tendon could be an early sign of peroneal tendonitis, especially if the patient has a history of repetitive ankle injuries or instability.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- Osteochondral fracture of the talus: Although the X-ray did not show an acute bony injury, it is essential to consider the possibility of an osteochondral fracture, which may not be visible on initial X-rays. This condition can lead to chronic pain, arthritis, and disability if not addressed promptly.
- Peroneal tendon rupture: While the ultrasound showed intact peroneal tendons, a rupture could be missed if the injury is complex or the ultrasound is not of high quality. A missed peroneal tendon rupture could lead to significant functional impairment and chronic instability.
- Rare diagnoses
- Accessory ossicle syndrome: The curvilinear density posterior to the talonavicular joint, likely representing an accessory ossicle, could potentially cause symptoms if it becomes inflamed or irritated. However, this is a less common cause of ankle pain and would require further evaluation to confirm.
- Stress fracture: Although the X-ray did not show an acute bony injury, a stress fracture could be considered, especially if the patient has a history of repetitive stress or overuse. However, this would be a less likely diagnosis given the acute presentation and ultrasound findings.