Finally, the internal structure of cartilage-bone interface was analyzed using the local binary patterns (LBP) based method. Furthermore, subchondral bone histological changes were specifically analyzed quantitatively with digital image analysis software by measuring the thickness of non-calcified and calcified cartilage as well as subchondral plate. This new grading system was correlated with the OARSI grading of overlying cartilage. In the present study, based on previous literature, we aimed to create a simple proposal of a histological grading system for changes occurring in subchondral bone during OA. Ultimately we believe that the histological features both of cartilage and bone should be incorporated into one standardized grading scale. Furthermore it could help us to link the changes in cartilage and bone for a better understanding of joint degeneration. Much like current histological cartilage OA grading scales (Mankin, OARSI), a standardized and easily adaptable scale for subchondral bone would make evaluating and reporting of histological data more consistent. There is indisputable evidence that subchondral bone remodeling is an essential part of OA pathogenesis but much less is known about the causality. We believe that the subchondral bone should not be disregarded in histological grading of OA. Furthermore, no literature can be found aiming to incorporate subchondral bone into complete histological assessment of OA. To our knowledge, there are no studies in which the subchondral bone histological changes have been directly correlated with OARSI grading system. They also suggested the changes of subchondral bone to be secondary to cartilage damage. Bone volume and trabecular thickness were found to increase, whereas trabecular number and separation decreased. Using four histomorphometric parameters (bone volume, trabecular thickness, trabecular number and trabecular separation) they found significant linear correlations between articular cartilage degeneration and subchondral bone changes. previously compared articular cartilage and subchondral bone histomorphometry in humans utilizing Mankin score. The defining feature of subchondral bone in late-stage OA is clearly increased bone volume and apparent density. As degeneration advances, changes in remodeling balance occur in four main processes: reduced bone turnover, subchondral sclerosis, thickening of calcified cartilage and thinning of trabeculae. In early OA, the mineral apposition rate of subchondral bone and bone remodeling increase and new remodeling sites arise, which leads to reduced thickness of the subchondral plate. Regardless of their omission in common histological evaluation, the changes that occur in subchondral bone in osteoarthritic joints have been widely recognized in literature. Despite its growing popularity, OARSI grading system is yet to be systematically compared with the changes in subchondral bone, especially in lower OARSI grades. OARSI grading system also accounts for some subchondral bone changes in the higher grades. A more novel, and presumably more consistent, Osteoarthritis Research Society International (OARSI) grading system focuses on the depth of cartilage degeneration and its extent over the whole joint surface. It focuses on architectural changes in articular cartilage and tidemark while also attending to cellular changes and proteoglycan content of cartilage. The first widely accepted and adopted histological OA grading system was the Mankin scoring. ![]() Diagnosis of OA is still mainly focused on detecting cartilage degeneration and skeletal changes are acknowledged only at later stages, even in histological assessment. The main methods of OA diagnostics are clinical evaluation by a physician, followed by radiography, magnetic resonance imaging (MRI), and in selected cases, arthroscopy. However, increasing evidence suggests that OA should be considered a disease of the whole joint unit and a gradual shift from cartilage-centered view towards a system biology approach can be seen. OA has traditionally been seen primarily as a disorder of the articular cartilage. In the United States alone, over 27 million adults are affected by OA and its prelevance is rising all the time. It is the most common form of arthritis and a significant factor in the public health of industrialized countries. Osteoarthritis (OA) is a progressive joint disorder characterized by the uneven and gradual degeneration of articular cartilage, joint pain, stiffness and loss of function in the absence of chronic autoimmune or autoinflammatory mechanisms.
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