Histologic Assessment of Medial and Lateral Menisci in Degenerative Knees Using Special Stains: A Histomorphometric...

Degenerative changes in meniscal tissue are increasingly recognized as key contributors to the initiation and progression of knee osteoarthritis (OA). Collagen, particularly type I collagen, forms the principal structural framework of the meniscus, and its degradation compromises meniscal function. Quantitative data on meniscal collagen content, especially comparing medial and lateral compartments in Indian OA patients, remain limited. This study aimed to evaluate and compare collagen content in medial and lateral menisci of osteoarthritic knees and correlate it with OA severity.

This hospital-based cross-sectional study included 50 patients undergoing total knee replacement for primary OA. Medial and lateral menisci were harvested, processed, and stained with Hematoxylin & Eosin and Masson's Trichrome. Collagen content was quantified using ImageJ software through colour deconvolution and threshold-based analysis, expressed as collagen area fraction (%). Histological degeneration was graded using a modified Pauli scoring system. Statistical analysis included paired t-test, Kruskal-Wallis test, and Spearman's correlation.

The medial meniscus showed significantly lower collagen content compared to the lateral meniscus (52.80 ± 4.30% vs 60.35 ± 5.84%; p < 0.001). Collagen percentage declined progressively with increasing OA severity in both compartments, with strong negative correlations between collagen content and OA grade (ρ =  - 0.887 medial; ρ =  - 0.951 lateral; p < 0.001). No significant associations were found with age, sex, or BMI.

Meniscal collagen depletion is marked in osteoarthritic knees, particularly in the medial compartment, and correlates strongly with disease severity. Masson's Trichrome staining combined with ImageJ morphometry provides a reliable method for objective assessment of meniscal degeneration and may aid in understanding OA progression.