What type of joint is characterized by being fully moveable with a synovial cavity?

A synovial joint is characterized by its ability to allow a wide range of movement due to the presence of a synovial cavity filled with synovial fluid. This fluid acts as a lubricant, reducing friction and enabling smooth movement between the articulating bones. Synovial joints also have a joint capsule that encases the joint, providing stability while allowing mobility. Examples of synovial joints include the knee, elbow, and shoulder, all of which can perform a variety of movements such as flexion, extension, rotation, and more.

In contrast, cartilaginous joints, which are joined by cartilage, allow for limited movement and do not have a synovial cavity. Fibrous joints are tightly connected by connective tissue, allowing for little to no movement. Saddle joints, while a specific type of synovial joint, do not represent the broader category that encompasses all fully moveable joints with synovial cavities.

Thus, synovial joints are the only type fully characterized by complete mobility and the presence of a synovial cavity, making this the correct choice.