Subchondral bone in osteoarthritis: insight into risk factors and microstructural changes.
Bottom Line: Importantly, we discuss risk factors influencing subchondral bone integrity.We also focus on the microarchitectural and histopathological changes of subchondral bone in OA, and provide an overview of their potential contribution to the progression of OA.A hypothetical model for the pathogenesis of OA is proposed.
Osteoarthritis (OA) is a major cause of disability in the adult population. As a progressive degenerative joint disorder, OA is characterized by cartilage damage, changes in the subchondral bone, osteophyte formation, muscle weakness, and inflammation of the synovium tissue and tendon. Although OA has long been viewed as a primary disorder of articular cartilage, subchondral bone is attracting increasing attention. It is commonly reported to play a vital role in the pathogenesis of OA. Subchondral bone sclerosis, together with progressive cartilage degradation, is widely considered as a hallmark of OA. Despite the increase in bone volume fraction, subchondral bone is hypomineralized, due to abnormal bone remodeling. Some histopathological changes in the subchondral bone have also been detected, including microdamage, bone marrow edema-like lesions and bone cysts. This review summarizes basic features of the osteochondral junction, which comprises subchondral bone and articular cartilage. Importantly, we discuss risk factors influencing subchondral bone integrity. We also focus on the microarchitectural and histopathological changes of subchondral bone in OA, and provide an overview of their potential contribution to the progression of OA. A hypothetical model for the pathogenesis of OA is proposed.
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Mentions: Despite the numerous pathophysiological alterations detected in subchondral bone withOA, we still lack a clear understanding of the mechanisms underpinning these phenomenaand how these different aspects are interrelated to each other. Based on the currentstate of knowledge, one hypothesis for the pathogenesis of OA emerges (Figure 5). Subchondral bone plays an important role in the pathogenesis ofOA, manifesting both microarchitectural and histopathological changes (BMELs, SBCs andmicrodamage). These histopathological changes not only have intimate interactions witheach other, but also have a close relationship with bone remodeling that wouldsubsequently lead to microarchitectural changes in the subchondral bone and theoverlying cartilage.