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A synovial joint, also known as diarthrosis, joins bones with a fibrous joint capsule that is continuous with the periosteum of the joined bones, constitutes the outer boundary of a synovial cavity, and surrounds the bones' articulating surfaces. The synovial (or joint) cavity is filled with synovial fluid. The joint capsule is made up of an outer layer, the articular capsule, which keeps the bones together structurally, and an inner layer, the synovial membrane, which seals in the synovial fluid. They are the most common and most movable type of joint in the body of a mammal. As with most other joints, synovial joints achieve movement at the point of contact of the articulating bones. == Structure == Synovial joints contain the following structures: * Synovial cavity: all diarthroses have the characteristic space between the bones that is filled with synovial fluid * Joint capsule: the fibrous capsule, continuous with the periosteum of articulating bones, surrounds the diarthrosis and unites the articulating bones; the joint capsule consists of two layers - (1) the outer fibrous membrane that may contain ligaments and (2) the inner synovial membrane that secretes the lubricating, shock absorbing, and joint-nourishing synovial fluid; the joint capsule is highly innervated, but without blood and lymph vessels, and receives nutrition from the surrounding blood supply via either diffusion (a slow process) or by convection, a far more efficient process achieved through exercise. * Articular cartilage: the bones of a synovial joint are covered by this layer of hyaline cartilage that lines the epiphyses of joint end of bone with a smooth, slippery surface that does not bind them together; articular cartilage functions to absorb shock and reduce friction during movement. Many, but not all, synovial joints also contain additional structures:〔 * Articular discs or menisci - the fibrocartilage pads between opposing surfaces in a joint * Articular fat pads - adipose tissue pads that protect the articular cartilage, as seen in the infrapatellar fat pad in the knee * Tendons〔 - cords of dense regular connective tissue composed of parallel bundles of collagen fibers * Accessory ligaments (extracapsular and intracapsular) - the fibers of some fibrous membranes are arranged in parallel bundles of dense regular connective tissue that are highly adapted for resisting strains to prevent extreme movements that may damage the articulation * Bursae - saclike structures that are situated strategically to alleviate friction in some joints (shoulder and knee) that are filled with fluid that is similar to synovial fluid〔 The bone surrounding the joint on the proximal side is sometimes called the ''plafond'', especially in the talocrural joint. A damage to this occurs in a Gosselin fracture. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Synovial joint」の詳細全文を読む スポンサード リンク
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