Meniscal flounce on knee MRI: correlation with meniscal locations after positional changes

Area of Science:

• Orthopedic imaging
• Knee biomechanics
• Magnetic Resonance Imaging (MRI)

Background:

• Meniscal flounce is an MRI finding of the meniscus.
• Its clinical significance and relationship to meniscal position are not fully understood.

Purpose of the Study:

• To illustrate the MRI features of meniscal flounce.
• To assess meniscal location changes on the tibial plateau with knee positioning.
• To evaluate the correlation between meniscal flounce and meniscal location.

Main Methods:

• Prospective study of 441 knee MRI scans over 8 months.
• Meniscal flounce assessed in routine 10-degree flexed knee MRI.
• Additional MR images obtained in maximal flexion and extension for 22 cases with flounce.
• Evaluated changes in flounce degree and meniscal location across positions.

Main Results:

• Meniscal flounce was observed in 5% (22/441) of medial menisci.
• Flounce disappeared in most cases with knee extension.
• Knee flexion showed varied effects: disappearance (41%), slight release (50%), or accentuation (9%).
• Meniscal horns migrated anteriorly with knee extension, with subtle posterior horn movement.

Conclusions:

• Active knee positioning alters meniscal flounce and meniscal location.
• Meniscal flounce is likely a transient physiologic distortion.
• The phenomenon may be related to meniscal position on the tibial plateau and is position-dependent.