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Posterior horn of lateral meniscus

The posterior horn of the lateral meniscus is the thickened posterior segment of the lateral meniscus in the knee joint. It plays an essential role in knee biomechanics, load distribution, shock absorption, and stabilization during flexion and rotation. The posterior horn is more mobile than the medial meniscus but is still prone to injury, particularly in sports or trauma involving twisting forces.

It is clinically important because tears in this region are common, sometimes subtle, and can be associated with anterior cruciate ligament (ACL) injuries or degenerative changes.

Synonyms

  • Posterior segment of the lateral meniscus

Location

  • Situated in the posterior aspect of the lateral tibial plateau

  • Lies between the posterior cruciate ligament (PCL) and the posterior horn of the medial meniscus

  • Extends from the midbody of the lateral meniscus to its posterior root attachment

Relations

  • Anteriorly: Midbody of the lateral meniscus

  • Posteriorly: Posterior capsule of the knee

  • Medially: Posterior cruciate ligament (PCL) and intercondylar notch

  • Laterally: Lateral femoral condyle and popliteus tendon

  • Inferiorly: Tibial plateau (lateral posterior part)

  • Superiorly: Femoral condyle cartilage

Function

  • Distributes axial load across the lateral compartment of the knee

  • Provides shock absorption during gait and activity

  • Enhances joint stability, particularly in flexion and rotation

  • Guides femoral condyle motion over the tibial plateau

  • Protects articular cartilage from excessive stress

Clinical Significance

  • Tears of the posterior horn of the lateral meniscus are common in athletes and can occur in isolation or with ACL tears

  • Degenerative changes in this region contribute to early osteoarthritis

  • Bucket-handle tears often involve the posterior horn

  • Arthroscopic evaluation of this region can be challenging due to its deep position

MRI Appearance

T1-weighted images:

  • Posterior horn appears as a low-signal triangular structure

  • Surrounded by intermediate signal of cartilage and bright fat in adjacent tissues

  • Tears may appear as linear or complex high-signal clefts extending to the articular surface

T2-weighted images:

  • Normal horn remains uniformly low signal

  • Tears appear as bright linear or complex signals within the dark meniscus extending to a surface

  • Associated parameniscal cysts or edema appear bright

STIR (Short Tau Inversion Recovery):

  • Normal horn is dark low signal

  • Pathology (tear, edema, inflammation) appears bright hyperintensity

  • Adjacent bone marrow edema in tibial plateau also bright

Proton Density Fat-Saturated (PD FS):

  • Meniscus remains low signal

  • Tears appear bright hyperintense, making this the most sensitive sequence for meniscal pathology

T1 Fat-Sat Post-Contrast:

  • Normal meniscus does not enhance

  • Tears, synovitis, or postsurgical scar may enhance at margins

3D T2 SPACE :

  • Meniscus appears as a low-signal crescent structure

  • Provides high-resolution depiction of horn morphology and tear configuration

MRI Arthrogram Appearance

  • Intra-articular gadolinium outlines the meniscus

  • Tear or root detachment: contrast extends into the meniscal substance or between meniscus and tibial plateau

  • Posterior horn tears highlighted by bright linear gadolinium signal crossing low-signal meniscus

CT Appearance

Non-Contrast CT:

  • Meniscus poorly visualized, seen only as a faint soft tissue density

  • Calcifications or ossicles may be visible if present

Post-Contrast CT:

  • Limited role in direct visualization of meniscus

  • Enhancement occurs in synovium or adjacent pathology, not in normal meniscus

CT Arthrogram Appearance

  • Meniscus sharply outlined by iodinated contrast

  • Normal posterior horn: appears as a triangular, well-defined filling defect

  • Tears: seen as contrast extension into the meniscal tissue or surface irregularities

  • Root tears visualized as separation between posterior horn root and tibial attachment

MRI image

Posterior horn of lateral meniscus sagittal cross sectional anatomy 3T MRI AI enhanced radiology anatomy image-img-00000-00000

MRI image

Posterior horn of lateral meniscus axial cross sectional anatomy 3T MRI AI enhanced radiology anatomy image-img-00000-00000

MRI image

Posterior horn of lateral meniscus coronal cross sectional anatomy 3T MRI AI enhanced radiology anatomy image-img-00000-00000