Ilan Elias MD, Presenter: Nothing to Disclose

Adam C. Zoga MD, Abstract Co-Author: Speakers Bureau, Bayer AG

Christopher Geordie Roth MD, Abstract Co-Author: Nothing to Disclose

Marcus P. Besser PhD, Abstract Co-Author: Nothing to Disclose

William B. Morrison MD, Abstract Co-Author: Medical Advisory Board, ONI Medical Systems, Inc

Meniscal extrusion greater than 3mm has been shown to be associated with underlying tear. We sought to evaluate the effect of axial load on the lower extremity for the MRI evaluation of medial meniscus extrusion in the knee.

50 patients (32F/18M, avg age 48, range 15-74) with clinical suspicion of medial meniscal tear had MR exams using a routine noncontrast knee protocol followed by repeat acquisition of sagittal PD FSE and coronal T2 FSE sequences after axial loading with an MRI compatible simulated weight-bearing device to 50% body weight. Pre and post loading sequences were evaluated by 2 MSK radiologists. Medial meniscus tears were recorded, medial meniscus extrusion (MME) was recorded and measured without and with simulated weight-bearing. Comparison between meniscus tear and non-tear groups were made.

20 of 50 (40%) had medial meniscus tear. There was a significant difference in MME in the overall population with and without axial load; mean MME without load was 2.06mm, 2.56mm with load (p<0.0001). There was a significant difference in MME in patients without tear (mean 0.4mm) versus those with tear (mean 3.2mm) on MRI without load (p<0.001). An increase in extrusion was noted for both groups on axial loaded MRI. For the medial meniscal tear group, mean MME increased from 3.2mm to 3.9mm with load (22% increase, p<0.001). For the group with no tear, mean MME without load was 0.4mm, 0.6mm with load (50% increase, p<0.05).

There is a significantly higher degree of medial meniscal extrusion with tear. However, medial meniscal extrusion increases with axial load independent of presence of underlying tear.

1) Meniscal extrusion is a potentially useful secondary sign of underlying tear. 2) Increase in medial meniscal displacement with axial load may help reveal clinically significant extrusion.  

Elias, I, Zoga, A, Roth, C, Besser, M, Morrison, W, Axial Loaded Knee MR Imaging for the Evaluation of Medial Meniscus Extrusion.  Radiological Society of North America 2009 Scientific Assembly and Annual Meeting, November 29 - December 4, 2009 ,Chicago IL. http://archive.rsna.org/2009/8016590.html