Presentation
Fall playing squash injuring right knee. Pain in the lateral aspect of knee.
Patient Data
Lateral compartment:
Avulsion fracture of the fibular head is noted with slightly displaced fractured fragments at the level of the arcuate ligament complex insertion.
The distal lateral collateral ligament and the arcuate ligament complex shows some high signal.
Medial compartment:
There is prominent bone marrow edema in the anteromedial aspect of the femoral and tibial condyles most likely in keeping with significant microtrabecular injury.
There is some thickening and minor high signal change at the femoral attachment of the medial collateral ligament in keeping with low-grade tear.
Case Discussion
This is the correspondent appearance of arcuate sign on MRI.
No concomitant cruciate ligament or popliteal tendon tear detected (unusual scenario in this type of injury).
There is no evidence of cortical disruption in the medial aspect, but the appearance of edema (significant microtrabecular injury) shows signs of early demarcation of a large bony fragment in the anterior aspect of the femoral condyle that may lead to osteochondral fracture later (best seen on coronal and sagittal sequences).