Meniscal Tears

Figure 1 – The menisci are located in the medial and lateral compartments of the knee. Their surfaces conform to the femoral and tibial contours. Both the medial meniscus and lateral meniscus have anterior and posterior bony attachment sites. Tears can result from trauma or degeneration. Common meniscal tear patterns (A, flap tear; B, radial tear; C, longitudinal tear) are shown. Collagen fiber bundles in the meniscus, which serve to absorb compressive loads, have a circumferential pattern, and radially oriented "tie fibers" provide structural rigidity (inset).

Figure 2 – This sagittal MRI scan depicts a grade 3 signal change within the medial meniscus (arrow) that is consistent with a tear.

Figure 3 – In this coronal MRI scan, a grade 3 signal change within the medial meniscus (arrow) consistent with a tear is shown.

Altered signals do not necessarily represent gross pathology (Table). In fact, abnormal signal has been found in up to 30% of asymptomatic patients who did not have a history of knee injury.6 A finding of solid meniscal tissue on 3 or more contiguous sagittal cuts suggests a diskoid meniscus. False-positive results occur more frequently than false-negative results, thus emphasizing the need for clinical correlation.

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