Osteoarthritis: More than Cartilage Degeneration

Osteoarthritis (OA) is nowadays considered as a global disease of the joint in which all articular structures are involved. Although articular cartilage is the primary target of the disease, both subchondral bone (SB) and synovium are structures that actively participate at the onset and in the progression of the disease. The relationship between these three structures is variable and mutable according to their evolution and the initial triggers. Pathogenic mechanisms will also vary depending on the predominant phenotype of OA in each patient. In this review, we emphasize the role of synovial membrane and SB in the onset and progression of the disease. Moreover, we review the current concepts of the cross talk between SB and articular cartilage and their biomechanical and functional properties. The participation of different structures in the OA pathogenesis will allow new therapeutic approaches directed to the main joint structures involved in every moment of the disease.