A degenerative medial meniscus retains some protective effect against osteoarthritis-induced subchondral bone changes

OBJECTIVES: The objective was to estimate the impact of the meniscus on cartilage and subchondral bone in knee osteoarthritis (OA). METHODS: In a sample of 46 knee specimens (26 females), 13 (7 females) were classified as OA according to the Kellgren-Lawrence classification. Outerbridge and meniscal grading were performed. Using micro-computed tomography images, we analyzed the cartilage thickness, subchondral plate thickness and micro-architecture of trabecular subchondral bone at different depths and in two different locations of the medial tibial plateau: one peripheral (PER) covered by the meniscus and one central (CENT) uncovered by the meniscus. RESULTS: Uncoverage by the meniscus was associated with bone sclerosis, defined as higher bone volume to total volume (BV/TV), higher trabecular number, thicker trabeculae with lower spacing, and anisotropy and a more plate-like architecture. The protective effect of meniscal coverage was observed in the uppermost 5 to 6 mm of the subchondral bone. As compared with normal knees, knees with OA showed significantly higher bone sclerosis (P <0.05–0.001) at the PER location, but only BV/TV (P=0.03) and trabecular number (P=0.02) differed between OA and non-OA knees at the CENT location uncovered by meniscus. CONCLUSIONS: OA results showed a partial dedifferentiation of the subchondral bone micro-architecture between PER and CENT locations probably due to menisci that still retain some of their protective effects on the subchondral bone.