Magnetic resonance analysis of loaded meniscus deformation: a novel technique comparing participants with and without radiographic knee osteoarthritis

Objective: To establish a novel method of quantifying meniscal deformation using loaded MRI. More specifically, the goals were to evaluate the (1) accuracy, (2) inter-rater reliability, (3) intra-rater reliability, and (4) scan-rescan reliability. The secondary purpose of this experiment was to evaluate group differences in meniscal deformation in participants with and without radiographic knee OA.

Materials and methods: Weight-bearing 3-T MRIs of the knee in full extension and 30° of flexion were processed to create 3D models of meniscal deformation. Accuracy was assessed using a custom-designed phantom. Twenty-one participants either with or without signs of OA were evaluated, and another six participants (14 knees, one subject was scanned twice) underwent repeated imaging to assess scan-rescan reproducibility. Intraclass correlation coefficient (ICC), root-mean squared error (RMSE), and root-mean-square percent coefficient-of-variation (RMS%CV) analyses were performed. Exploratory comparisons were made between those with and without OA to evaluate potential group differences.

Results: All variables were found to be accurate with RMSE ranging from 0.08 to 0.35 mm and 5.99 to 14.63 mm². Reproducibility of peak anterior-posterior meniscal deformation was excellent (ICC > 0.821; p < 0.013) with RMS%CV for intra-rater ranging from 0.06 to 1.53 % and 0.17 to 1.97 %, inter-rater ranging from 0.10 to 7.20 % and 3.95 to 18.53 %, and scan-rescan reliability ranging from 1.531 to 7.890 % and 4.894 to 9.142 %, for distance and area metric, respectively. Participants with OA were found to have significantly greater anterior horn movement of both the medial (p = 0.039) and lateral meniscus (p = 0.015), and smaller flexed medial meniscus outer area (p = 0.048) when compared to controls.

Conclusions: MRI-based variables of meniscus deformation were found to be valid in participants with and without OA. Significant differences were found between those with and without radiographic OA; further study is warranted.