This sagittal proton-density weighted, fat-saturated image of the right knee shows linear high signal (click image for arrow) in the posterior horn of the lateral meniscus. The high signal extends to the articular surface, consistent with a longitudinal tear. There is some high signal in the anterior horn which probably extends to the articular surface and may represent extension of the tear anteriorly.
A longitudinal tear is a vertical tear around the long axis of the meniscus. Other types of vertical tear include flap tears and radial tears. A longitudinal tear usually begins in the posterior horn and is typically peripherally located. Isolated anterior horn longitudinal tears are rare. The typical MRI finding is high signal on short TE sequences which extends to the articular surface (either inferior or superior). If fluid extends into the tear there will also be high signal on T2-weighted sequences.
Reference: Stoller et al. Diagnostic Imaging: Orthopaedics. 1st edition. Amirsys 2004.
Credit: Dr Laughlin Dawes