Diarthrosen

Diarthroses, also known as synovial joints, are the most common type of joint in the body, characterized by the presence of a joint cavity filled with synovial fluid. This fluid acts as a lubricant, reducing friction between the articulating bones and allowing for smooth, free movement. The articulating surfaces of the bones are covered with articular cartilage, a smooth, elastic tissue that further cushions and protects the ends of the bones.

A key feature of diarthroses is the joint capsule, a fibrous connective tissue that encloses the joint cavity and helps to stabilize the joint. This capsule is lined by the synovial membrane, which produces the synovial fluid. Ligaments, strong bands of fibrous tissue, also surround and reinforce the joint capsule, preventing excessive movement and dislocation.

Diarthroses are further classified based on the type of movement they permit. For example, hinge joints, like those in the elbow and knee, allow for flexion and extension. Ball-and-socket joints, found in the shoulder and hip, permit a wide range of motion in multiple directions. Pivot joints, such as those between the atlas and axis vertebrae, allow for rotational movement. Gliding joints, found in the wrists and ankles, permit slight sliding or gliding movements. Saddle joints, like the thumb's carpometacarpal joint, allow for opposition and a wide range of movement. Condyloid joints, present in the wrist, allow for flexion, extension, abduction, and adduction.