Meniscus Tears and MRI Diagnosis
The menisci of the knee are paired crescent-shaped fibrocartilaginous structures — the medial and lateral menisci — that reside between the femoral condyles and the tibial plateau. Their primary roles are to distribute axial loads across the knee joint, absorb shock, and protect the articular cartilage and subchondral bone from excessive stress[^c1]. The medial meniscus has an open C-shape covering approximately 60% of the medial tibial plateau, while the lateral meniscus is more circular, covering approximately 80% of the lateral tibial plateau and bearing a greater proportion of the compartmental load. Both menisci appear as homogeneous low-signal-intensity structures on all MRI pulse sequences due to their dense fibrocartilaginous composition and lack of mobile protons[^c5].
Meniscal tears are among the most prevalent sports-related knee injuries, with an estimated incidence of 60 per 100,000 people[^c4]. They can result from acute traumatic events — typically twisting injuries in young athletes producing vertical longitudinal tears — or from progressive myxoid degeneration of the meniscal matrix in older individuals, which produces horizontal or complex tears. Bucket-handle tears, a severe subtype of vertical longitudinal tear with displacement of the inner meniscal fragment, account for 10–19% of all meniscal tears and frequently cause mechanical locking of the knee. Meniscal damage is directly linked to early degenerative osteoarthritis, as removal of meniscal tissue increases articular cartilage loads by 235% in the lateral compartment and 75% in the medial compartment[^c6].
Magnetic resonance imaging is the modality of choice for evaluating meniscal pathology, offering high sensitivity and specificity without ionizing radiation[^c3]. A meta-analysis of 13 studies reported a pooled sensitivity of 87% and specificity of 82% for MRI detection of meniscal tears, with an area under the curve of 0.93[^c2]. Standard protocols employ proton-density and T2-weighted sequences in three orthogonal planes with slice thickness of 3 mm or less. The hallmark diagnostic criterion is linear high signal within the normally low-signal meniscus that extends to an articular surface, confirmed on two or more consecutive images. Multiple secondary signs, including parameniscal cysts, meniscal extrusion, and subchondral bone marrow edema, increase diagnostic confidence when the tear itself is subtle.
The clinical management of meniscal tears has evolved substantially, shifting from routine meniscectomy toward meniscus-preserving strategies whenever possible. Tear pattern, location relative to the vascularized peripheral zone, and patient age guide the decision between repair and partial meniscectomy. Among athletes, meniscal repair yields return-to-sport rates of 96%, compared to 50% after meniscectomy. Post-operative rehabilitation protocols — including tear-type-specific weight-bearing, range-of-motion, and return-to-sport timelines — are detailed in [[Meniscal Surgery Rehabilitation]]. Accurate MRI characterization of tear morphology, displacement, and associated injuries is essential for preoperative planning, making the radiologist's role central to the multidisciplinary care of patients with meniscal pathology.