Refractive index of human articular cartilage varies with tissue structure and composition

Optical properties of biological tissues, such as refractive index, are fundamental properties, intrinsically linked to a tissue's composition and structure. This study aims to investigate the variation of refractive index (RI) of human articular cartilage along the tissue depth (via collagen fibril orientation and optical density) and integrity (based on Mankin and Osteoarthritis Research Society International (OARSI) scores). The results show the relationship between RI and PG content (p = 0.042), collagen orientation (p = 0.037), and OARSI score (p = 0.072). When taken into account, the outcome of this study suggests that the RI of healthy cartilage differs from that of patho-logical cartilage (p = 0.072). This could potentially provide knowledge on how progressive tissue degeneration, such as osteoarthritis, affects changes in cartilage RI, which can, in turn, be used as a potential optical biomarker of tissue pathology. (c) 2023 Optica Publishing Group