Diarthroz

Diarthroz refers to diarthrosis, the class of joints in the animal body that are freely movable. In standard anatomy, diarthrosis or synovial joints are distinguished by a joint cavity and a surrounding articular capsule that, together with synovial fluid, permits substantial mobility while distributing loads. The term diarthroz is sometimes encountered as a variant spelling or transliteration of diarthrosis in older or non-English sources.

Anatomy and function

A diarthrotic joint comprises a synovial capsule, an inner synovial membrane, and an outer fibrous capsule. The articulating surfaces are covered with articular cartilage and separated by a synovial cavity filled with lubricating fluid. Ligaments, tendons, and muscles surrounding the joint provide stability and control movement. The joint capsule and synovial membrane supply nutrition and lubrication, reducing wear on the articular cartilage. Nerve fibers and blood vessels enable proprioception and reflex responses that coordinate movement.

Types and examples

There are six primary forms of synovial joints: ball-and-socket (shoulder, hip), hinge (elbow, knee), pivot (proximal radioulnar joint), condyloid (wrist), saddle (thumb), and plane (acromioclavicular and intertarsal joints). Each type allows different axes and ranges of motion, from simple flexion–extension to multi-axis rotation and sliding movements.

Clinical relevance

Diarthroses enable most voluntary limb movements and complex coordination. They are subject to degenerative and inflammatory conditions, such as osteoarthritis and rheumatoid arthritis, which can affect mobility and cause pain. Dislocations or ligament injuries commonly involve diarthrotic joints and may require medical management or intervention.