This is Barry Belosis, one of the musculoskeletal radiology fellows at Stanford University. 18-year-old male football player presents for evaluation on the sideline after injury on his left knee. Concerned for lateral collar ligament injury and posterior lateral corner injury. The patient in this case presented with this knee radiograph. Here in our AP radiograph we can see a non-displaced fracture, the fibular head is seen here, and also seen on this image right here. Stress views are sometimes done to evaluate for asymmetric widening of the knee joint. The patient in this case underwent various stress tests demonstrating this asymmetric widening in the lateral compartment as we can see here compared to the contralateral side. However, various stress testing is not part of the routine workup in patients with knee injury in the emergency setting. The patient also underwent MRI knee without contrast. Here on our coronal T1 imaging we can see just subtle hypo-intensity along the expected course of the fibular collar ligament. And on our axial PD fat set imaging we can see this edema just superficial to the fibular collar ligament and also likely deep to the fibrous right here which is suggestive of underlying sprain. Additionally, we can see this edema just at the posterior lateral corner concerning for underlying posterior lateral corner injury. Here on our sagittal T2 fat set and PD imaging we can see that there is bone contusion in the medial femoral condyle and medial tibial plateaus we see here. On our sagittal PD here we could not see any discrete fracture line. On our coronal T2 fat set imaging again we can see this bone contusion in the medial femoral condyle and the tibial plateau and some sprain injury to the fibular collar ligament which would have been expected in this region. This is on a different patient. Here a quick review of our normal medial collar ligament. We can see a dark band arising from the distal femur to the tibia without any irregularity. This is in comparison to this partial tear of the MCL on the other patient. We can see this irregular proximal medial collar ligament. In our fluid sensitive images we can see that there is edema superficial, deep and within the fibrous itself consistent with grade 2 sprain. Grade 1 sprain would demonstrate abnormal signal just superficial to the ligament itself. Again this is on a different patient. Here on our coronal T2 fat set imaging we can see that there is indistinct and not visualized lateral collar ligament at the femoral attachment right here. On our T1 imaging we can see that there is no longer hypo intense band at the expected location of the fibular collar ligament. These findings are consistent with grade 3 sprain or a high grade sprain.

2nd Edition, CASE 31

2nd Edition

Knee

knee injury

fibular head fracture

collateral ligament sprain

posterior lateral corner injury

bone contusion