Vacuum phenomenon simulating meniscal or cartilaginous injury of the knee at MR imaging.

In five patients undergoing magnetic resonance imaging of the knee after athletic injuries, the authors identified a vacuum phenomenon that simulated medial meniscal or joint compartment cartilaginous abnormality. A cadaveric knee was injected with air, and the findings were re-created. The presence of air or gas between the articular surfaces of the tibia and femur can simulate meniscal or cartilaginous injury.