The arcuate sign is a well described finding of fibular head avulsion at the insertion site of the arcuate complex. It has been associated with posterolateral corner knee injury and resulting instability. The authors report two patients presenting with the arcuate sign following knee dislocation, which has not been previously described. As unrecognized spontaneously reduced knee dislocation often results in significant morbidity, the authors propose that the arcuate sign should raise clinical suspicion of this injury mechanism.