Meniscal Flounce on Knee MRI: Correlation with Meniscal Locations After Positional Changes

Objective: The purpose of our study was to illustrate the MRI features of meniscal flounce and the meniscal locations on the tibial plateau after positional changes without external force and to evaluate the correlation of the presence of flounce with meniscal location.

Subjects And Methods: For 8 months, 441 knee MR images were prospectively studied for meniscal flounce. Routine MRI was performed on a 10 degrees flexed knee, and flounce was seen in 22 medial menisci (5%). In all 22 of the patients with flounce, additional sagittal proton density-weighted MR images were obtained while the knees were both maximally flexed and maximally extended in a knee surface coil. We evaluated and compared the changes of degree of flounce and meniscal location on the tibial plateau among the three positions.

Results: With the maximally extended knee, the flounce disappeared in all cases but one. With the maximally flexed knee, the flounce disappeared in nine cases (9/22, 41%), was slightly released in 11 (11/22, 50%), and was accentuated in two (2/22, 9%). As the knees were more extended, the anterior horns of the menisci migrated more anteriorly, the posterior horns revealed subtle movement without a regular pattern, and the flounce was slightly released or disappeared.

Conclusion: Active knee positioning in the knee surface coil changed the degree of meniscal flounce and the meniscal location on the tibial plateau. The meniscal flounce is thought to be a transient physiologic distortion and may be related to meniscal locations on the tibial plateau. It may be changed by varying the knee position.