Characterizing Bovine Meniscus Wear Using PLM and Brightfield Imaging

Meniscal degeneration is a leading cause of knee osteoarthritis, affecting 55% of individuals over age 70. Our current research investigates the structural integrity of worn menisci; however, techniques to evaluate fiber fraying and degenerative changes at the superficial surface are limited. The objective of this research was to develop methods to characterize these changes at the superficial layer of bovine meniscus previously subjected to varying loading magnitudes. Brightfield (BF) and polarized-light microscopy (PLM) were used to image the worn meniscus samples (n = 3 per specimen; n = 153 total). Using our custom 0-4 scoring system, three trained individuals graded fiber fraying severity from BF images, where scores for each specimen were summed to determine an overall fraying grade (grade 1-4). The thickness of the superficial layer was assessed from PLM images using custom criteria to ensure consistency. The application of the grading scale resulted in strong inter-rater and intra-rater agreement (ICC = 0.92 and 0.90 to 0.93, respectively). The PLM measurements indicated decreasing layer thickness with increasing loading magnitudes, although inter-rater agreement was low (ICC = 0.012). This study advances characterization of meniscus degenerative changes through microscopy techniques, enhancing future research on meniscus wear responses through histological assessment.