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. The menisci transmit 50–70% of the knee joint load in extension and up to 85% at 90 degrees of flexion, converting axial forces into circumferential hoop stresses via their type I collagen fiber network anchored by meniscal root ligaments[^c8]. Both menisci appear as homogeneous low-signal-intensity structures on all MRI pulse sequences due to their dense fibrocartilaginous composition[^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 on a semi-flexed weight-bearing knee in young athletes — or from progressive myxoid degeneration of the meniscal matrix in older individuals. The pediatric population shows a rising incidence (5.1 per 100,000 athletes) driven by increasingly intense sports participation at younger ages, with lateral meniscal tears more common in children and a distinct tear distribution pattern. 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]. MRI has a reported sensitivity of 85–95% and specificity of 85–90% for detecting meniscal tears[^c14]. An updated 2026 meta-analysis of 75 studies reported higher pooled sensitivity for medial than lateral tears (91.0% versus 78.5%), with higher specificity for lateral tears[^c17]; American College of Radiology guidance cites 96% sensitivity and 97% specificity at 3T[^c18]. Compartment-level accuracy differs in clinical series, with lateral meniscal tears demonstrating lower sensitivity but higher specificity than medial tears[^c20]. Standard protocols employ proton-density and T2-weighted sequences in three orthogonal planes with slice thickness of 3 mm or less, and recent advances in simultaneous multi-slice acquisition and deep learning reconstruction have enabled accelerated protocols achieving 7-minute five-sequence exams with preserved diagnostic accuracy (medial meniscus sensitivity 89–95%). Advanced three-dimensional isotropic sequences provide thin-slice, gap-free volumetric data with multiplanar reformation capabilities, with diagnostic performance comparable to or better than conventional 2D imaging[^c22]. The hallmark diagnostic criterion is linear high signal within the normally low-signal meniscus that extends unequivocally to the articular surface, confirmed on two consecutive slices in the same plane or on slices in two different planes[^c7]. Multiple secondary signs, including parameniscal cysts, meniscal extrusion, and subchondral bone marrow edema, increase diagnostic confidence when the tear itself is subtle. Where MRI is contraindicated or unavailable, ultrasound provides a first-line alternative with pooled sensitivity of 88% and specificity of 90%, although its performance is operator-dependent[^c19].
The 2026 interdisciplinary Delphi consensus on standardized meniscus MRI reporting has established a shared language for radiologists and orthopedic surgeons, mandating precise anatomic terminology for tear location and pattern while prohibiting terms such as "stable," "unstable," "reparable," and "unrepairable" in imaging reports, as these imply surgical judgments that imaging alone cannot determine[^c9]. Artificial intelligence models have demonstrated diagnostic performance comparable to physicians (average AUC 0.91), and deep learning assistance has been shown to improve radiologist sensitivity for medial meniscus tears, suggesting a growing role for AI as a clinical decision support tool. A 2024 meta-analysis found that AI models reliably detect the presence of a meniscal tear but are less accurate at localizing tears to specific regions of the meniscus (AUC 0.939 versus 0.905)[^c21]. In 2025, a hybrid CNN-Transformer model integrating MobileNetV2 and Swin Transformer achieved 99.94% accuracy on a meniscal tear detection dataset, highlighting the potential of lightweight architectures for automated classification[^c12].
Recent developments in 2026 include the characterization of five distinct morphological subtypes of the posterior horn medial meniscus periphery, improving ramp lesion detection in ACL-deficient knees; the description of the "rising tide sign" for differentiating intra-articular gas from true meniscal pathology; studies showing moderate MRI accuracy (71–72%) for meniscal tear detection in ACL-deficient knees with pattern-specific variability; and a detailed analysis of anterior horn lateral meniscus (AHLM) tear morphologies, which found that radial AHLM tears occur more frequently in younger male patients and are more often managed surgically[^c10][^c11]. In pediatric patients with ACL tears, MRI has a limited sensitivity of 62.3% for meniscal injury detection, with nearly a quarter of injuries going unrecognized on preoperative imaging[^c13]. The largest pediatric meniscal repair cohort to date (1,185 repairs from the SCORE registry) has characterized sex-, age-, and BMI-associated differences in tear patterns[^c16]. Post-operative rehabilitation has been refined with tear-type-specific weight-bearing protocols stratified by tear morphology and supported by a formal EU-US multi-society consensus.
The clinical management of meniscal tears has evolved substantially, shifting from routine meniscectomy toward meniscus-preserving strategies whenever possible. Three landmark randomized controlled trials (FIDELITY, METEOR, ESCAPE) have consistently shown that non-operative management is equivalent to surgery for degenerative meniscal tears, and long-term follow-up has demonstrated accelerated osteoarthritis progression after meniscectomy. 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. Accurate MRI characterization of tear morphology, displacement, and associated injuries — including ramp lesions, root tears, and concomitant ligamentous injuries — is essential for preoperative planning, making the radiologist's role central to the multidisciplinary care of patients with meniscal pathology.