Internal-Control-Normalized T2 Mapping of Meniscal Abnormalities on a Cartilage MRI Protocol: An Exploratory Retrospective Study

Background/Objectives: Meniscal pathology is a common consequence of knee injury and a precursor of osteoarthritis, but qualitative MRI grading cannot reliably distinguish low-grade intrasubstance degeneration from more advanced pathology. Quantitative T2 relaxation value (T2RV) mapping is an established cartilage marker, but internal-control normalisation within the same meniscus has not been formalised for incidental meniscal pathology. We hypothesised that pathologic meniscal regions would show elevated T2RV relative to internal-control tissue. Methods: In this retrospective, single-centre study, 61 pathologic meniscal lesions with arthroscopic correlation (12 tears, 40 repaired, 9 myxoid/intrasubstance degeneration) in 55 patients (mean age 47.1 ± 8.8 years) underwent a cartilage T2RV MRI protocol. A pathologic and a remote internal-control region of interest (ROI) were placed on the T2RV colour map for each lesion; the T2RV endpoint was (pathologic − internal-control ROI T2RV)/internal-control ROI T2RV × 100%. Groups were compared using Wilcoxon signed-rank and Kruskal–Wallis (Dunn’s post hoc) tests and multivariable linear regression. Results: Pathologic ROI T2RV exceeded internal-control ROI T2RV (p < 0.001; mean elevation 55.7%). The endpoint varied among pathology groups (p < 0.001): degeneration showed the smallest elevation (17.5%), while repair (60.0%) and tear (69.9%) were similarly higher and indistinguishable, remaining independently associated with a higher endpoint than degeneration after multivariable adjustment. Longer postoperative intervals were associated with a lower endpoint among repaired lesions (β = −6.27 points/100 days). Conclusions: Internal-control-normalised T2RV mapping is a promising quantitative marker of meniscal tissue status that may complement conventional MRI and clinical assessment, with T2RV elevation differing among myxoid/intrasubstance degeneration, tear, and repaired meniscus within this cohort. Prospective, multicenter validation is warranted before clinical adoption.