Disease Processes of Synovial Membrane, Fibrous Capsule, Ligaments, and Articular Cartilage

The joint should be considered as an organ made up of critical tissues, all of which can be affected in the disease process of osteoarthritis: the joint capsule (with its components of fibrous joint capsule and synovial membrane), intra-articular and capsular ligaments, articular cartilage, and subchondral bone (Fig. 1). The fibrous portion of the joint capsule is composed of dense fibrous connective tissue that provides some mechanical stability to the joint. The collateral ligaments are associated with the joint capsule. Intra-articular ligaments normally have a synovial membranea cover. The fibrous portion of the joint capsule and the ligaments are principally composed of collagenous fibers and type I collagen predominates in these fibrous connective tissues of the joint. The insertions of the fibrous capsule and articular ligaments into the adjacent bones demonstrate a zonal organization. Parallel bundles of collagen first become invested with the fibrocartilaginous stroma and as they near the bone become calcified. The collagenous fibers enter the bone cortex in a manner analogous to Sharpey’s fibers. This gradual transition of joint capsule and ligaments to mineralized fibrocartilage and then to bone enhances the ability of the insertions to distribute forces evenly and decrease the likelihood of pullout failure.