Age / Sex : 55 / F

Age / Sex : 55/F

Chief complaint : Left knee pain

medial meniscal root (radial) tear

Discussion

Findings:

Sagittal T1-weighted image shows a diffuse hyperintense signal intensity (arrow) in posterior medial meniscal root. A band-like hyperintense signal intensity (arrow) is seen  in posterior medial meniscal root on coronal T2-weighted image and axial fat-suppressed proton density-weighted image.

Diagnosis:  

Medial meniscal root (radial) tear

Discussion:

The posterior meniscal roots are critical attachment sites of the medial and lateral menisci to the central tibial plateau and occur adjacent to the tibial insertions of the anterior and posterior cruciate ligaments. The medial meniscus takes more force during weight bearing than the lateral meniscus and the posterior horn and the body of the medial meniscus take most of the force applied to the medial compartment of the knee and are the least mobile parts. Without firm insertion of the tibia, the medial meniscus tends to subluxate medially and lose some of its tension, affecting the ability of the meniscus to absorb and dissipate loads through hoop stresses. Medial meniscal root tears result in medial meniscus extrusion and subsequent development of accelerated medial compartment osteoarthritis. Posterior meniscal root tears can be easily missed due to the inconsistent clinical symptoms and may be overlooked without thorough arthroscopic examination.

Superior-view drawing denoting tibial insertion sites of menisci in relationship to cruciate ligaments: medial meniscus (MM), lateral meniscus (LM), posterior cruciate ligament (P), anterior crucitate ligament (A), posterior root of medial meniscus (black arrow), posterior root of lateral meniscus (white arrow), anterior root of medial meniscus (black arrowhead), and anterior root of lateral meniscus (white arrowhead).

References:
1.  Brody JM, Hulstyn MJ, Fleming BC, Tung GA. The meniscal roots: gross anatomic correlation with 3-T MRI findings. AJR 2007;188:W446-W450