22-year-old female with acute ankle pain after an inversion trauma. There is marked swelling and a large hematoma around the lateral ankle, with additional medial discoloration. The patient walks with crutches, wears a brace, and demonstrates a clear antalgic, largely non-weight-bearing gait pattern. Previous radiographs showed no fracture.
Ultrasound examination of the ankle demonstrates rupture of the anterior talofibular ligament. The appearance is consistent with a full-thickness, partial-width rupture: part of the ligament remains intact, but the majority of the fibres are interrupted.
The calcaneofibular ligament is continuous and therefore not completely ruptured. However, it is thickened, swollen, and hypoechoic, compatible with a severe strain or partial sprain without complete discontinuity.
The anterior tibiofibular ligament appears intact. During dynamic or loaded ultrasound examination, no clear widening of the ankle mortise is visible, and there are no sonographic signs of syndesmotic instability.
There is marked posttraumatic soft tissue swelling and hematoma formation around the ankle. The previous negative radiograph makes an obvious fracture less likely, although ultrasound is not suitable for precise fracture diagnosis and is limited for assessing intra-articular pathology such as cartilage injury or osteochondral lesions.
1. Final diagnosis
Severe lateral ankle ligament injury after inversion trauma, with a full-thickness, partial-width rupture of the anterior talofibular ligament. The calcaneofibular ligament remains intact but shows clear strain or sprain-related changes. No sonographic evidence of anterior tibiofibular ligament rupture or dynamic syndesmotic instability is present.
2. Differential diagnosis
The primary diagnosis is a severe lateral ankle sprain with dominant injury of the anterior talofibular ligament and associated strain of the calcaneofibular ligament. If pain persists or recovery is delayed, differential diagnoses include occult bone injury, osteochondral lesion of the talus, intra-articular synovial irritation, peroneal tendon pathology, or injury of the medial ligament complex, especially given the medial discoloration. Syndesmotic injury is less likely based on the current dynamic ultrasound examination, but should be reconsidered clinically if high ankle pain, pain during external rotation stress, or poor recovery progression develops.
3. Teaching points
Ultrasound can directly assess the lateral ankle ligaments after inversion trauma and can distinguish between complete discontinuity and partial-width ligament rupture. Dynamic assessment is useful when evaluating possible syndesmotic instability. Marked swelling and hematoma are common after severe ankle sprain and may contribute to pain inhibition and reduced weight-bearing. A negative radiograph reduces the likelihood of an obvious fracture but does not exclude occult bone injury or osteochondral pathology.
4. Injury/disease information
The anterior talofibular ligament is the most commonly injured ligament in inversion ankle trauma. The calcaneofibular ligament may be strained or partially injured in more severe sprains. Functional treatment usually includes bracing, temporary use of crutches when needed, swelling control, gradual pain-guided weight-bearing, restoration of gait, range of motion, proprioception, and progressive strengthening. Persistent inability to bear weight, deep joint pain, locking, marked residual swelling, recurrent instability, or delayed recovery may require reassessment and MRI to evaluate occult bone, cartilage, intra-articular, tendon, or additional ligament injury.
Marc is founder of, and trainer at, SonoSkills. SonoSkills is an organization dedicated to MSK ultrasound education. He's also an MSK Sonographer at EchoConsult in Roermond, the Netherlands.
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